<table><caption>TABLE 47 Allergens in Fruits (source: IUIS Allergen Database, Dec 2021; www.allergen.org). Molecular weight and IgE-prevalences are listed according to WHO/IUIS Allergen Nomenclature Sub-Committee Website (www.allergen.org), unless otherwise referenced.</caption><thead><tr><th>Allergen source</th><th>Allergen</th><th>Biochemical name</th><th>MW (kDa)</th><th>IgE prevalence/ Sensitisation</th></tr></thead><tbody><tr><td colspan="5"><strong>ROSALES</strong></td></tr><tr><td rowspan="4">Apple<br>(Malus domestica)</td><td>Mal d 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>17</td><td>15-70% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 2</td><td>Thaumatin-like protein (TLP)</td><td>23</td><td>5-18% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 3</td><td>Non specific lipid transfer<br>protein (nsLTP type 1)</td><td>9</td><td>1-50% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 4</td><td>Profilin</td><td>14</td><td>10-40% of apple allergic patients <sup>36</sup></td></tr><tr><td rowspan="5">Peach<br>(Prunus persica)</td><td>Pru p 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>17</td><td>11% of peach allergic pediatric cohort <sup>1147</sup><br>7-13% in adults (Spain, IT) <sup>1129, 1148</sup></td></tr><tr><td>Pru p 2</td><td>TLP</td><td>23</td><td>Not available</td></tr><tr><td>Pru p 3</td><td>nsLTP</td><td>9</td><td>96% of peach allergic children <sup>1147</sup></td></tr><tr><td>Pru p 4</td><td>Profilin</td><td>14</td><td>10% peach allergic children (Spain), 7-34%<br>adults (Spain, IT <sup>1147, 1148</sup></td></tr><tr><td>Pru p 7</td><td>Gibberellin regulated protein (GRP)</td><td>7</td><td>62-65% peach allergic adults (FR, PN) <sup>231, 1130</sup></td></tr><tr><td colspan="5"><strong>ERICALES</strong></td></tr><tr><td rowspan="13">Green Kiwifruit<br>(Actinidia deliciosa)</td><td>Act d 1</td><td>Actinidin</td><td>30</td><td>5-32% (Central Europe - Iceland) <sup>1149</sup></td></tr><tr><td>Act d 2</td><td>TLP</td><td>23</td><td>2-18% <sup>1707</sup></td></tr><tr><td>Act d 3</td><td>glycoprotein</td><td>40</td><td>Not available</td></tr><tr><td>Act d 4</td><td>Phytocystatin</td><td>11</td><td>Not available</td></tr><tr><td>Act d 5</td><td>Kiwellin</td><td>28</td><td>2-18% <sup>1148, 1707</sup></td></tr><tr><td>Act d 6</td><td>Pectin methylesterase inhibitor</td><td>18</td><td>Not available</td></tr><tr><td>Act d 7</td><td>Pectin methylesterase</td><td>50</td><td>Not available</td></tr><tr><td>Act d 8</td><td>PR-10</td><td>17</td><td>7-58% <sup>1163, 1707</sup></td></tr><tr><td>Act d 9</td><td>Profilin</td><td>14</td><td>7-31% <sup>1707</sup></td></tr><tr><td>Act d 10</td><td>nsLTP type 1</td><td>10</td><td>3-2% <sup>1149</sup></td></tr><tr><td>Act d 11</td><td>Major latex protein/ripening-related protein<br>(MLP/RRP), Bet v 1 family member</td><td>17</td><td>24%</td></tr><tr><td>Act d 12</td><td>Cupin, 11S globulin</td><td>50</td><td>71%</td></tr><tr><td>Act d 13</td><td>2S albumin</td><td>11</td><td>18%</td></tr><tr><td colspan="5"><strong>SAPINDALES</strong></td></tr><tr><td rowspan="4">Sweet orange<br>(Citrus sinensis)</td><td>Cit s 1</td><td>Germin like protein</td><td>23</td><td>78% <sup>1674</sup></td></tr><tr><td>Cit s 2</td><td>Profilin</td><td>14</td><td>96% <sup>1674</sup></td></tr><tr><td>Cit s 3</td><td>nsLTP type 1</td><td>9</td><td>Not available</td></tr><tr><td>Cit s 7</td><td>Gibberellin regulated protein (GRP)</td><td>7</td><td>86% <sup>1130</sup></td></tr><tr><td colspan="5"><strong>ZINGIBERALES</strong></td></tr><tr><td rowspan="6">Banana<br>(Musa a - acuminata)</td><td>Mus a 1</td><td>Profilin</td><td>14</td><td>44% (small cohort)</td></tr><tr><td>Mus a 2</td><td>Class I chitinase</td><td>33</td><td>Only few cases reported</td></tr><tr><td>Mus a 3</td><td>nsLTP type 1</td><td>9</td><td>20%</td></tr><tr><td>Mus a 4</td><td>TLP</td><td>20</td><td>72%</td></tr><tr><td>Mus a 5</td><td>Beta-1,3-glucanase</td><td>30</td><td>74-84% in a pediatric cohort</td></tr><tr><td>Mus a 6</td><td>Ascorbate peroxidase</td><td>27</td><td>Only few cases reported</td></tr><tr><td colspan="5"><strong>CUCURBITALES</strong></td></tr><tr><td rowspan="3">Melon<br>(Cucumis melo)</td><td>Cuc m 1</td><td>Alkaline serine protease (cucumisin)</td><td>67</td><td>Not available</td></tr><tr><td>Cuc m 2</td><td>Profilin</td><td>14</td><td>Only few cases reported</td></tr><tr><td>Cuc m 3</td><td>Pathogenesis-related protein PR-1</td><td>17</td><td>Only few cases reported</td></tr></tbody></table>
<table><caption>TABLE 47 Allergens in Fruits (source: IUIS Allergen Database, Dec 2021; www.allergen.org). Molecular weight and IgE-prevalences are listed according to WHO/IUIS Allergen Nomenclature Sub-Committee Website (www.allergen.org), unless otherwise referenced.</caption><thead><tr><th>Allergen source</th><th>Allergen</th><th>Biochemical name</th><th>MW (kDa)</th><th>IgE prevalence/ Sensitisation</th></tr></thead><tbody><tr><td colspan="5"><strong>ROSALES</strong></td></tr><tr><td rowspan="4">Apple<br>(Malus domestica)</td><td>Mal d 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>17</td><td>15-70% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 2</td><td>Thaumatin-like protein (TLP)</td><td>23</td><td>5-18% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 3</td><td>Non specific lipid transfer<br>protein (nsLTP type 1)</td><td>9</td><td>1-50% of apple allergic patients <sup>36</sup></td></tr><tr><td>Mal d 4</td><td>Profilin</td><td>14</td><td>10-40% of apple allergic patients <sup>36</sup></td></tr><tr><td rowspan="5">Peach<br>(Prunus persica)</td><td>Pru p 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>17</td><td>11% of peach allergic pediatric cohort <sup>1147</sup><br>7-13% in adults (Spain, IT) <sup>1129, 1148</sup></td></tr><tr><td>Pru p 2</td><td>TLP</td><td>23</td><td>Not available</td></tr><tr><td>Pru p 3</td><td>nsLTP</td><td>9</td><td>96% of peach allergic children <sup>1147</sup></td></tr><tr><td>Pru p 4</td><td>Profilin</td><td>14</td><td>10% peach allergic children (Spain), 7-34%<br>adults (Spain, IT <sup>1147, 1148</sup></td></tr><tr><td>Pru p 7</td><td>Gibberellin regulated protein (GRP)</td><td>7</td><td>62-65% peach allergic adults (FR, PN) <sup>231, 1130</sup></td></tr><tr><td colspan="5"><strong>ERICALES</strong></td></tr><tr><td rowspan="13">Green Kiwifruit<br>(Actinidia deliciosa)</td><td>Act d 1</td><td>Actinidin</td><td>30</td><td>5-32% (Central Europe - Iceland) <sup>1149</sup></td></tr><tr><td>Act d 2</td><td>TLP</td><td>23</td><td>2-18% <sup>1707</sup></td></tr><tr><td>Act d 3</td><td>glycoprotein</td><td>40</td><td>Not available</td></tr><tr><td>Act d 4</td><td>Phytocystatin</td><td>11</td><td>Not available</td></tr><tr><td>Act d 5</td><td>Kiwellin</td><td>28</td><td>2-18% <sup>1148, 1707</sup></td></tr><tr><td>Act d 6</td><td>Pectin methylesterase inhibitor</td><td>18</td><td>Not available</td></tr><tr><td>Act d 7</td><td>Pectin methylesterase</td><td>50</td><td>Not available</td></tr><tr><td>Act d 8</td><td>PR-10</td><td>17</td><td>7-58% <sup>1163, 1707</sup></td></tr><tr><td>Act d 9</td><td>Profilin</td><td>14</td><td>7-31% <sup>1707</sup></td></tr><tr><td>Act d 10</td><td>nsLTP type 1</td><td>10</td><td>3-2% <sup>1149</sup></td></tr><tr><td>Act d 11</td><td>Major latex protein/ripening-related protein<br>(MLP/RRP), Bet v 1 family member</td><td>17</td><td>24%</td></tr><tr><td>Act d 12</td><td>Cupin, 11S globulin</td><td>50</td><td>71%</td></tr><tr><td>Act d 13</td><td>2S albumin</td><td>11</td><td>18%</td></tr><tr><td colspan="5"><strong>SAPINDALES</strong></td></tr><tr><td rowspan="4">Sweet orange<br>(Citrus sinensis)</td><td>Cit s 1</td><td>Germin like protein</td><td>23</td><td>78% <sup>1674</sup></td></tr><tr><td>Cit s 2</td><td>Profilin</td><td>14</td><td>96% <sup>1674</sup></td></tr><tr><td>Cit s 3</td><td>nsLTP type 1</td><td>9</td><td>Not available</td></tr><tr><td>Cit s 7</td><td>Gibberellin regulated protein (GRP)</td><td>7</td><td>86% <sup>1130</sup></td></tr><tr><td colspan="5"><strong>ZINGIBERALES</strong></td></tr><tr><td rowspan="6">Banana<br>(Musa a - acuminata)</td><td>Mus a 1</td><td>Profilin</td><td>14</td><td>44% (small cohort)</td></tr><tr><td>Mus a 2</td><td>Class I chitinase</td><td>33</td><td>Only few cases reported</td></tr><tr><td>Mus a 3</td><td>nsLTP type 1</td><td>9</td><td>20%</td></tr><tr><td>Mus a 4</td><td>TLP</td><td>20</td><td>72%</td></tr><tr><td>Mus a 5</td><td>Beta-1,3-glucanase</td><td>30</td><td>74-84% in a pediatric cohort</td></tr><tr><td>Mus a 6</td><td>Ascorbate peroxidase</td><td>27</td><td>Only few cases reported</td></tr><tr><td colspan="5"><strong>CUCURBITALES</strong></td></tr><tr><td rowspan="3">Melon<br>(Cucumis melo)</td><td>Cuc m 1</td><td>Alkaline serine protease (cucumisin)</td><td>67</td><td>Not available</td></tr><tr><td>Cuc m 2</td><td>Profilin</td><td>14</td><td>Only few cases reported</td></tr><tr><td>Cuc m 3</td><td>Pathogenesis-related protein PR-1</td><td>17</td><td>Only few cases reported</td></tr></tbody></table>
<figure><img src="image_213.png" /></figure>

FIGURE 101 Celery and tomato as selected examples of vegetable allergen sources. Proteins belonging to the PR-10 family are depicted in yellow, nsLTPs in green (type 1 in light green and type 2 in dark green); profilins in red; cyclophilin and defensin like protein in light grey FAD oxidase and beta-fructofuranosidase in dark grey

4 – Clinical relevance, diagnosis, and management

Although a number of well characterized components are available to facilitate the *in vitro* diagnosis in fruit and vegetable allergies, some important ones are still lacking<sup>1154</sup> (the components offered for allergen specific *in vitro* diagnosis are indicated in the Appendix). To date the following proteins are used for CRD: cross-reactive allergens derived from inhalant allergenic sources (Bet v 1 and Bet v 2 from birch pollen and the latex allergens Hev b 6.01, 6.02, and 11) as well as food components from Rosaceae fruits (Mal d 1,2,3,4; Pru av 1,3,4; Pru p 1,3,4,7; Fra a 1,3).<sup>36,999,1148,1155</sup> kiwifruit allergens (Act d 1,2,5,8,10; Act d 11), Apiaceae allergens (Dau c 1, Api g 1,2,6) and some tomato (Sola I 6) and potato (Sola t 1) allergens. Therefore, the following section focuses on Rosaceae, Apiaceae, kiwifruit allergy and the latex-fruit-syndrome.

Clinical relevance and clinical pattern

Rosaceae fruit allergy (Figure 102)

The Rosaceae family includes many edible fruits. Apple, cherry and peach are the best-studied species from an allergy point of view. Allergen components are available to date just from peach and apple. The allergens identified in the fruits of the Rosaceae family are 1) PR-10 (Bet v 1 family member, 2) profilin, 3) nsLTP type 1, 4) gibberellin-regulated protein and 5) thaumatin like protein. Due to high cross-reactivity between the PR-10 proteins, the profilins and the nsLTPs, the corresponding allergens derived from peach are usually applied for diagnostic approaches in all types of Rosaceae fruit allergies.

The Sensitization pattern to these allergens is geographically influenced. sensitization rates to the Bet v 1 homologous proteins are significantly higher in countries with high pollen exposure of the Fagales trees (birch, alder, hazel; see chapters B01 and C02), whereas sensitization to nsLTP is significantly higher in Mediterranean countries (see chapter C03).<sup>36,1146,1156</sup> sensitization to Rosaceae fruit profilins (chapter C01) is more evenly distributed but most likely higher in the Mediterranean area.<sup>36</sup> sensitization to gibberellin-regulated protein has been described in Southern France and correlated with exposure to cypress pollen.<sup>231,1157</sup>

Data on sensitization to thaumatin-like proteins in fruits are lim-
ited. Bet v 1-(PR-10) related food proteins, profilin and nsLTP are
pan-allergens, depicting a high cross-reactivity across the plant king-
dom and sensitization to these molecules is often not accompanied

by clinical symptoms.<sup>1158,1159</sup> Therefore, determination of slgE to
these molecules should not be used as a screening tool (no prophetic
testing!) and sensitization without convincing case history should al-
ways be validated by food challenge. All three protein families have
been associated with the various types of clinical manifestations in
Rosaceae fruit allergies ranging from contact urticaria of the oral
mucosa (so called Oral Allergy Syndrome, OAS) up to anaphylaxis.
The prevalence of systemic reactions in those patients with a con-
firmed fruit allergy is higher in nsLTP-mediated fruit allergies than in
the Bet v 1 or profilin-mediated ones.<sup>34,36,1156</sup> In the following, three
typical patterns of Rosaceae fruit allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to Bet v 1 homologous proteins from different Rosaceae fruits. Symptoms are elicited by unprocessed fruits. The usual manifestations are local oropharyngeal symptoms (OAS). *Caveat*: in selected cases Bet v 1 (PR-10) related fruit allergy can be associated with systemic reaction,<sup>1160</sup> i.e., in conjunction with co-factors (alcohol, exercise, NSAID intake, ingestion on an empty stomach<sup>1162</sup> or high quantity of the ingested Bet v 1 homologues).

B Patient with a sensitization to nsLTP mainly derived from peach (Pru p 3) may develop cross-sensitization to other fruit nsLTPs. The clinical manifestations vary from local oropharyngeal symptoms up to anaphylaxis. The clinical pattern is influenced by co-factors (see under A), so called LTP syndrome.<sup>1157</sup> Symptoms are elicited by unprocessed and processed fruits.

C Patients with a sensitization to profilin, frequently acquired via sensitization to grass pollen, might develop a cross-sensitization to profilin in Rosaceae fruits.³⁶ Sensitization to profilin is highly likely to be clinically silent but can elicit in a minor subset of patients local oropharyngeal symptoms (OAS). The risk for a systemic reaction is very low but has been described in patients with epithelial barrier damage of the oral mucosa in a Mediterranean area.³³⁹ *Caveat*: sensitization to *profilin* is highly likely to be *clinically asymptomatic*.

Kiwifruit allergy

Allergy to kiwifruit is one of the most frequently observed
fruit allergies in Europe.<sup>1149</sup> Thirteen kiwifruit allergens have
<figure><img src="image_213.png" /></figure>

FIGURE 101 Celery and tomato as selected examples of vegetable allergen sources. Proteins belonging to the PR-10 family are depicted in yellow, nsLTPs in green (type 1 in light green and type 2 in dark green); profilins in red; cyclophilin and defensin like protein in light grey FAD oxidase and beta-fructofuranosidase in dark grey

4 – Clinical relevance, diagnosis, and management

Although a number of well characterized components are available to facilitate the *in vitro* diagnosis in fruit and vegetable allergies, some important ones are still lacking<sup>1154</sup> (the components offered for allergen specific *in vitro* diagnosis are indicated in the Appendix). To date the following proteins are used for CRD: cross-reactive allergens derived from inhalant allergenic sources (Bet v 1 and Bet v 2 from birch pollen and the latex allergens Hev b 6.01, 6.02, and 11) as well as food components from Rosaceae fruits (Mal d 1,2,3,4; Pru av 1,3,4; Pru p 1,3,4,7; Fra a 1,3).<sup>36,999,1148,1155</sup> kiwifruit allergens (Act d 1,2,5,8,10; Act d 11), Apiaceae allergens (Dau c 1, Api g 1,2,6) and some tomato (Sola I 6) and potato (Sola t 1) allergens. Therefore, the following section focuses on Rosaceae, Apiaceae, kiwifruit allergy and the latex-fruit-syndrome.

Clinical relevance and clinical pattern

Rosaceae fruit allergy (Figure 102)

The Rosaceae family includes many edible fruits. Apple, cherry and peach are the best-studied species from an allergy point of view. Allergen components are available to date just from peach and apple. The allergens identified in the fruits of the Rosaceae family are 1) PR-10 (Bet v 1 family member, 2) profilin, 3) nsLTP type 1, 4) gibberellin-regulated protein and 5) thaumatin like protein. Due to high cross-reactivity between the PR-10 proteins, the profilins and the nsLTPs, the corresponding allergens derived from peach are usually applied for diagnostic approaches in all types of Rosaceae fruit allergies.

The Sensitization pattern to these allergens is geographically influenced. sensitization rates to the Bet v 1 homologous proteins are significantly higher in countries with high pollen exposure of the Fagales trees (birch, alder, hazel; see chapters B01 and C02), whereas sensitization to nsLTP is significantly higher in Mediterranean countries (see chapter C03).<sup>36,1146,1156</sup> sensitization to Rosaceae fruit profilins (chapter C01) is more evenly distributed but most likely higher in the Mediterranean area.<sup>36</sup> sensitization to gibberellin-regulated protein has been described in Southern France and correlated with exposure to cypress pollen.<sup>231,1157</sup>

Data on sensitization to thaumatin-like proteins in fruits are lim-
ited. Bet v 1-(PR-10) related food proteins, profilin and nsLTP are
pan-allergens, depicting a high cross-reactivity across the plant king-
dom and sensitization to these molecules is often not accompanied

by clinical symptoms.<sup>1158,1159</sup> Therefore, determination of slgE to
these molecules should not be used as a screening tool (no prophetic
testing!) and sensitization without convincing case history should al-
ways be validated by food challenge. All three protein families have
been associated with the various types of clinical manifestations in
Rosaceae fruit allergies ranging from contact urticaria of the oral
mucosa (so called Oral Allergy Syndrome, OAS) up to anaphylaxis.
The prevalence of systemic reactions in those patients with a con-
firmed fruit allergy is higher in nsLTP-mediated fruit allergies than in
the Bet v 1 or profilin-mediated ones.<sup>34,36,1156</sup> In the following, three
typical patterns of Rosaceae fruit allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to Bet v 1 homologous proteins from different Rosaceae fruits. Symptoms are elicited by unprocessed fruits. The usual manifestations are local oropharyngeal symptoms (OAS). Caveat: in selected cases Bet v 1 (PR-10) related fruit allergy can be associated with systemic reaction,<sup>1160</sup> i.e., in conjunction with co-factors (alcohol, exercise, NSAID intake, ingestion on an empty stomach<sup>1162</sup> or high quantity of the ingested Bet v 1 homologues).

B Patient with a sensitization to nsLTP mainly derived from peach (Pru p 3) may develop cross-sensitization to other fruit nsLTPs. The clinical manifestations vary from local oropharyngeal symptoms up to anaphylaxis. The clinical pattern is influenced by co-factors (see under A), so called LTP syndrome.<sup>1157</sup> Symptoms are elicited by unprocessed and processed fruits.

C Patients with a sensitization to profilin, frequently acquired via sensitization to grass pollen, might develop a cross-sensitization to profilin in Rosaceae fruits.³⁶ Sensitization to profilin is highly likely to be clinically silent but can elicit in a minor subset of patients local oropharyngeal symptoms (OAS). The risk for a systemic reaction is very low but has been described in patients with epithelial barrier damage of the oral mucosa in a Mediterranean area.³³⁹ *Caveat*: sensitization to *profilin* is highly likely to be *clinically asymptomatic*.

Kiwifruit allergy

Allergy to kiwifruit is one of the most frequently observed
fruit allergies in Europe.<sup>1149</sup> Thirteen kiwifruit allergens have
been identified to date (Table 47). An allergy to kiwifruit can be acquired via gastrointestinal tract (primary food allergy) or via cross-sensitization to birch or grass pollen and latex allergens. The allergic symptoms range from mild oropharyngeal symptoms to severe, generalized reactions. Actinidin, Act d 1, is the major allergen of kiwifruit and correlates significantly with a kiwifruit monosensitization.¹¹⁵⁰ Sensitization to Act d 8 and Act d 9 is specific for patients with pollen-kiwifruit allergies.¹¹⁵⁰,¹¹⁶³ The sequence homology between kiwifruit nsLTP (Act d 10) and other nsLTPs, particularly Pru p 3 from peach, is low and therefore there is a limited risk of cross-reactivity. Additionally, cross-reactivity between Hev b 11, a chitinase from latex, and a protein in kiwifruit has been identified. The sensitivity of IgE measurement to kiwifruit extract is low (17%) but could be increased by including different kiwifruit components (Act d 1-Act d 5 and Act d 8 Act d 9) to 77%.¹¹⁵⁰ Sensitization to Act d 1 was associated with the severity of the reaction¹¹⁴⁹ in a pan-European study and sensitizations to Act d 1 and Act d 3 were significantly correlated with anaphylactic reactions of patients from Spain.¹¹⁵⁵ In the following four typical patterns of kiwi allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to the Bet v 1 homologous protein Act d 8. The usual manifestations are local oropharyngeal symptoms (OAS).

B Patient with a sensitization to profilin particularly from grass pollen may develop cross-sensitization to profilin in kiwifruit. The usual manifestations are local oropharyngeal symptoms (OAS).

C Patient with a sensitization to latex proteins (i.e., Hev b 6 and 11) may develop cross-sensitization to homologous proteins in kiwifruit. The clinical pattern varies from mild oropharyngeal symptoms up to anaphylaxis.

D Patients with a sensitization (usually monosensitization) to Act d 1 may develop a primary kiwifruit allergy. The risk to develop systemic reaction up to anaphylaxis is increased.

## Apiaceae vegetable allergy

The major representatives of the Apiaceae family in terms of food allergy are celeriac (Apium graveolens) and carrot (Daucus carota). Celeriac allergy is highly associated with birch pollen and mugwort pollen sensitization referred to as birch-mugwort-celery-syndrome.

To date, 5 relevant celeriac allergens have been identified in celeriac tuber, Api g 1 (Bet v 1 homologue), Api g 2 (nsLTP type 1), Api g 4 (profilin), Api g 5 (flavoprotein) and Api g 7, the defensin like protein 1 (www.allergen.org). In addition Api g 6, an nsLTP type 2 protein was identified in celery stalk. The application of Api g 1, 4, 5 in component resolved diagnosis, increased the sensitivity from approximately 70% to 88% (75% rApi g 1, 42% rApi g 4 and 42% to nApi g 5).¹¹⁵² Celeriac-induced symptoms range from mild oropharyngeal symptoms (OAS) to anaphylaxis.¹¹⁶⁵ No marker allergen for prediction of severe reactions has yet been identified. Particularly severe reactions to celeriac occur in mugwort-sensitized patients.¹¹⁵²,¹¹⁶⁵ The culprit cross-reactive

allergens between mugwort and celeriac have not been identified so far. The clinical significance of the nsLTPs derived either from celeriac tuber (Api g 6) or from celery stalk (Api g 2) has not been confirmed to date.¹¹⁴³,¹⁷⁰⁸

Also carrot allergy is highly associated with a sensitization to birch and mugwort pollen¹¹⁵³. Allergens identified in carrot are Dau c 1 (PR-10), Dau c 4 (profilin), Dau c 5 (isoflavone reductase), Dau c CyP (cyclophilin) and Dau c nsLTP. The diagnostic relevance of Dau c 5 and Dau c CyP has not been investigated and it is not clear whether Dau c nsLTP is indeed present in the edible parts of carrots. As for celeriac allergy, carrot allergy induced symptoms ranging from mild oropharyngeal symptoms (OAS) to anaphylaxis.¹¹⁵³ In the following two typical patterns of celeriac/carrot allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to Bet v 1 homologous proteins in Apiaceae vegetables such as carrot and celeriac. Symptoms are often elicited by unprocessed foods. The usual manifestations are local oropharyngeal symptoms (OAS).

Caveat: Bet v 1 (PR-10) related allergy to carrot and celeriac can be associated with systemic reaction. Systemic reactions are more frequently observed in PR-10-related celeriac and carrot allergy than in PR-10 related allergy to Rosaceae fruits¹¹⁶⁵ and might be elicited also by processed foods (particularly in celeriac allergy).¹¹⁶⁶

B Patient with a sensitization to mugwort pollen may develop cross-sensitization to not yet defined allergens in celeriac and carrot. The clinical manifestation varies from local oropharyngeal symptoms up to anaphylaxis. Symptoms are elicited by unprocessed and processed vegetables. IgE determination and skin testing particularly to celeriac extract are often negative. Typical pattern: Sensitization to mugwort pollen, positive prick-prick test with native food, negative testing using celeriac extract.

## Latex-fruit syndrome

In 30-70% of patients with latex associated food allergies have been observed, particularly to banana, avocado, chestnut, kiwifruit (see kiwifruit allergy), and many more.¹⁶⁶⁵ Eleven percent of patients with a fruit allergy showed symptoms after latex challenge.¹¹⁶⁸ Oropharyngeal symptoms are frequently observed, but in about 10% of latex-associated food allergies, anaphylactic reactions have been observed. As cross-reactive allergens beta-1,3-glucanase (Hev b 2), hevein (Hev b 6.02) and the hevein-like domain of class I chitinases (Hev b 11) have been identified. However, further studies are needed since the pathogenic role of Hev b 6 and Hev b 11 have been questioned in a recent study.¹¹⁶⁹ Further information is provided in Chapter B22.

## Cannabis-food syndrome

Cannabis sativa is a plant belonging to the Cannabaceae family. Hemp is a variety of *C. sativa* grown for industrial use. The nsLTP Can s 3 is suspected to be the major cross-reacting allergen in the so called cannabis-food syndrome. In patients with cannabis-induced anaphylaxis, Can s 3 was the major allergen and 72% reported to suffer from a systemic food allergy, in part co-factor mediated.¹¹⁷⁰
been identified to date (Table 47). An allergy to kiwifruit can be acquired via gastrointestinal tract (primary food allergy) or via cross-sensitization to birch or grass pollen and latex allergens. The allergic symptoms range from mild oropharyngeal symptoms to severe, generalized reactions. Actinidin, Act d 1, is the major allergen of kiwifruit and correlates significantly with a kiwifruit monosensitization.¹¹⁵⁰ Sensitization to Act d 8 and Act d 9 is specific for patients with pollen-kiwifruit allergies.¹¹⁵⁰,¹¹⁶³ The sequence homology between kiwifruit nsLTP (Act d 10) and other nsLTPs, particularly Pru p 3 from peach, is low and therefore there is a limited risk of cross-reactivity. Additionally, cross-reactivity between Hev b 11, a chitinase from latex, and a protein in kiwifruit has been identified. The sensitivity of IgE measurement to kiwifruit extract is low (17%) but could be increased by including different kiwifruit components (Act d 1-Act d 5 and Act d 8 Act d 9) to 77%.¹¹⁵⁰ Sensitization to Act d 1 was associated with the severity of the reaction¹¹⁴⁹ in a pan-European study and sensitizations to Act d 1 and Act d 3 were significantly correlated with anaphylactic reactions of patients from Spain.¹¹⁵⁵ In the following four typical patterns of kiwi allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to the Bet v 1 homologous protein Act d 8. The usual manifestations are local oropharyngeal symptoms (OAS).

B Patient with a sensitization to profilin particularly from grass pollen may develop cross-sensitization to profilin in kiwifruit. The usual manifestations are local oropharyngeal symptoms (OAS).

C Patient with a sensitization to latex proteins (i.e., Hev b 6 and 11) may develop cross-sensitization to homologous proteins in kiwifruit. The clinical pattern varies from mild oropharyngeal symptoms up to anaphylaxis.

D Patients with a sensitization (usually monosensitization) to Act d 1 may develop a primary kiwifruit allergy. The risk to develop systemic reaction up to anaphylaxis is increased.

## Apiaceae vegetable allergy

The major representatives of the Apiaceae family in terms of food allergy are celeriac (*Apium graveolens*) and carrot (*Daucus carota*). Celeriac allergy is highly associated with birch pollen and mugwort pollen sensitization referred to as birch-mugwort-celery-syndrome.

To date, 5 relevant celeriac allergens have been identified in celeriac tuber, Api g 1 (Bet v 1 homologue), Api g 2 (nsLTP type 1), Api g 4 (profilin), Api g 5 (flavoprotein) and Api g 7, the defensin like protein 1 (www.allergen.org). In addition Api g 6, an nsLTP type 2 protein was identified in celery stalk. The application of Api g 1, 4, 5 in component resolved diagnosis, increased the sensitivity from approximately 70% to 88% (75% rApi g 1, 42% rApi g 4 and 42% to nApi g 5).¹¹⁵² Celeriac-induced symptoms range from mild oropharyngeal symptoms (OAS) to anaphylaxis.¹¹⁶⁵ No marker allergen for prediction of severe reactions has yet been identified. Particularly severe reactions to celeriac occur in mugwort-sensitized patients.¹¹⁵²,¹¹⁶⁵ The culprit cross-reactive

allergens between mugwort and celeriac have not been identified so far. The clinical significance of the nsLTPs derived either from celeriac tuber (Api g 6) or from celery stalk (Api g 2) has not been confirmed to date.¹¹⁴³,¹⁷⁰⁸

Also carrot allergy is highly associated with a sensitization to birch and mugwort pollen¹¹⁵³. Allergens identified in carrot are Dau c 1 (PR-10), Dau c 4 (profilin), Dau c 5 (isoflavone reductase), Dau c CyP (cyclophilin) and Dau c nsLTP. The diagnostic relevance of Dau c 5 and Dau c CyP has not been investigated and it is not clear whether Dau c nsLTP is indeed present in the edible parts of carrots. As for celeriac allergy, carrot allergy induced symptoms ranging from mild oropharyngeal symptoms (OAS) to anaphylaxis.¹¹⁵³ In the following two typical patterns of celeriac/carrot allergy are outlined.

A Patient with a sensitization to Fagales tree pollen and IgE to Bet v 1 may develop cross-sensitization to Bet v 1 homologous proteins in Apiaceae vegetables such as carrot and celeriac. Symptoms are often elicited by unprocessed foods. The usual manifestations are local oropharyngeal symptoms (OAS).

Caveat: Bet v 1 (PR-10) related allergy to carrot and celeriac can be associated with systemic reaction. Systemic reactions are more frequently observed in PR-10-related celeriac and carrot allergy than in PR-10 related allergy to Rosaceae fruits¹¹⁶⁵ and might be elicited also by processed foods (particularly in celeriac allergy).¹¹⁶⁶

B Patient with a sensitization to mugwort pollen may develop cross-sensitization to not yet defined allergens in celeriac and carrot. The clinical manifestation varies from local oropharyngeal symptoms up to anaphylaxis. Symptoms are elicited by unprocessed and processed vegetables. IgE determination and skin testing particularly to celeriac extract are often negative. Typical pattern: Sensitization to mugwort pollen, positive prick-prick test with native food, negative testing using celeriac extract.

## Latex-fruit syndrome

In 30-70% of patients with latex associated food allergies have been observed, particularly to banana, avocado, chestnut, kiwifruit (see kiwifruit allergy), and many more.¹⁶⁶⁵ Eleven percent of patients with a fruit allergy showed symptoms after latex challenge.¹¹⁶⁸ Oropharyngeal symptoms are frequently observed, but in about 10% of latex-associated food allergies, anaphylactic reactions have been observed. As cross-reactive allergens beta-1,3-glucanase (Hev b 2), hevein (Hev b 6.02) and the hevein-like domain of class I chitinases (Hev b 11) have been identified. However, further studies are needed since the pathogenic role of Hev b 6 and Hev b 11 have been questioned in a recent study.¹¹⁶⁹ Further information is provided in Chapter B22.

## Cannabis-food syndrome

Cannabis sativa is a plant belonging to the Cannabaceae family. Hemp is a variety of *C. sativa* grown for industrial use. The nsLTP Can s 3 is suspected to be the major cross-reacting allergen in the so called cannabis-food syndrome. In patients with cannabis-induced anaphylaxis, Can s 3 was the major allergen and 72% reported to suffer from a systemic food allergy, in part co-factor mediated.¹¹⁷⁰
<table><caption>TABLE 48 Allergens in Vegetables (source: IUIS Allergen Database, (www.allergen.org Dec 2021). Molecular weight and IgE-prevalences are listed according to WHO/IUIS Allergen Nomenclature Sub-Committee Website (www.allergen.org), unless otherwise referenced.</caption><thead><tr><th>Allergen source</th><th>Allergen</th><th>Biochemical name</th><th>MW (kDa)</th><th>IgE prevalence/ Sensitisation</th></tr></thead><tbody><tr><td colspan="5"><strong>APIALES</strong></td></tr><tr><td rowspan="6">Celery<br>(Apium graveolens)</td><td>Api g 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>16</td><td>75% <sup>1152, 1165</sup></td></tr><tr><td>Api g 2</td><td>nsLTP type 1</td><td>9</td><td>26%</td></tr><tr><td>Api g 4</td><td>Profilin</td><td>14</td><td>42% BP risk factor; <sup>1152, 1165</sup></td></tr><tr><td>Api g 5</td><td>FAD-containing oxidase</td><td>58</td><td>45% <sup>1152</sup></td></tr><tr><td>Api g 6</td><td>nsLTP type 2</td><td>7</td><td>38%</td></tr><tr><td>Api g 7</td><td>Defensin like protein 1</td><td>12</td><td>50% <sup>1144</sup></td></tr><tr><td rowspan="3">Carrot<br>(Daucus carota)</td><td>Dau c 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>16</td><td>58-100% <sup>1153</sup></td></tr><tr><td>Dau c 4</td><td>Profilin</td><td>14</td><td>18% risk factor pollen profilin sensitisation <sup>1153</sup></td></tr><tr><td>Dau c 5</td><td>Isoflavone reductase-like protein</td><td>33</td><td>6-20% <sup>1153</sup></td></tr><tr><td colspan="5"><strong>SOLANALES</strong></td></tr><tr><td rowspan="6">Tomato<br>(Solanum<br>lycopersicum)</td><td>Sola l 1</td><td>Profilin</td><td>14</td><td>32%</td></tr><tr><td>Sola l 2</td><td>Beta-fructofuranosidase</td><td>50</td><td>4/10 patients with CCD sensitisation</td></tr><tr><td>Sola l 3</td><td>nsLTP type 1</td><td>9</td><td>Not available</td></tr><tr><td>Sola l 4</td><td>Pathogenesis-related protein, PR-10, TSI-1</td><td>20</td><td>76%; Bet v 1 sensitisation risk factor</td></tr><tr><td>Sola l 5</td><td>Cyclophilin</td><td>19</td><td>Not available</td></tr><tr><td>Sola l 6</td><td>nsLTP type 2</td><td>7</td><td>71%</td></tr><tr><td rowspan="4">Potato<br>(Solanum tuberosum)<br>all data linked<br>to potato</td><td>Sola t 1</td><td>Patatin</td><td>43</td><td>74% in a small pediatric cohort</td></tr><tr><td>Sola t 2</td><td>Cathepsin D inhibitor PDI</td><td>21</td><td>51% in a small pediatric cohort</td></tr><tr><td>Sola t 3</td><td>Cysteine protease inhibitor</td><td>21</td><td>58% in a small pediatric cohort</td></tr><tr><td>Sola t 4</td><td>Serine protease inhibitor 7</td><td>16</td><td>67% in a small pediatric cohort</td></tr><tr><td colspan="5"><strong>LAURALES</strong></td></tr><tr><td>Avocado<br>(Persea americana)</td><td>Pers a 1</td><td>Chitinase class 1</td><td>32</td><td>75%</td></tr><tr><td colspan="5"><strong>ROSALES</strong></td></tr><tr><td rowspan="4">Indian hemp<br>(Cannabis sativa)</td><td>Can s 2</td><td>Profilin</td><td>14</td><td>16% (mixed exposure: airways and ingestion)</td></tr><tr><td>Can s 3</td><td>nsLTP type 1</td><td>9</td><td>72%</td></tr><tr><td>Can s 4</td><td>Oxygen evolving Enhancer Protein 2</td><td>27</td><td>No data published yet</td></tr><tr><td>Can s 5</td><td>PR-10 homologue</td><td>18</td><td>78% (airway exposure -BP allergy risk factor)</td></tr></tbody></table>

However, further studies are needed. The content of the psychoactive component tetrahydrocannabinol (THC) is higher in *C sativa* than in hemp. Different parts of the plant can induce allergic reactions such as hemp seeds¹¹⁷¹ used in food industry or marijuana (dried flowering tops and leaves) and hashish (dried resin), both frequently consumed drugs.¹¹⁷² Furthermore, (occupational) allergy to Cannabis has been described reviewed in.¹¹⁷³ Cannabis allergy manifestations range from cutaneous contact urticaria to anaphylaxis. The allergens described so far in *C sativa* are Can s 3,¹¹⁷⁴ a nsLTP, Can s 5,¹¹⁷⁵ a Bet v 1 homologue, the cannabis profilin Can s 2 and Can s 4.¹¹⁷⁶ In a recent study, among 25 patients with immediate symptoms on

exposure to cannabis, 52% were sensitized to Can s 3, 80% to Can s 5 and 16% to Can s 2.¹¹⁷⁵ Only 7% of patients with a Cannabis allergy were sensitized to Can s 4 in another study.¹¹⁷⁶ The nsLTP, Can s 3, is suspected to be the major cross-reacting allergen in the so called cannabis-food syndrome. In patients with cannabis-induced anaphylaxis, Can s 3 was the major allergen and 72% reported to suffer from a systemic food allergy, in part co-factor mediated.¹¹⁷⁰

### Clinical diagnosis of fruit and vegetable allergies

Allergies to fruits and vegetables are often initiated by a primary sensitization to pollen. Since the majority of fruit and vegetable allergens belong to a few protein families and are characterized by a
<table><caption>TABLE 48 Allergens in Vegetables (source: IUIS Allergen Database, (www.allergen.org Dec 2021). Molecular weight and IgE-prevalences are listed according to WHO/IUIS Allergen Nomenclature Sub-Committee Website (www.allergen.org), unless otherwise referenced.</caption><thead><tr><th>Allergen source</th><th>Allergen</th><th>Biochemical name</th><th>MW (kDa)</th><th>IgE prevalence/ Sensitisation</th></tr></thead><tbody><tr><td colspan="5"><strong>APIALES</strong></td></tr><tr><td rowspan="6">Celery<br>(Apium graveolens)</td><td>Api g 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>16</td><td>75% <sup>1152, 1165</sup></td></tr><tr><td>Api g 2</td><td>nsLTP type 1</td><td>9</td><td>26%</td></tr><tr><td>Api g 4</td><td>Profilin</td><td>14</td><td>42% BP risk factor; <sup>1152, 1165</sup></td></tr><tr><td>Api g 5</td><td>FAD-containing oxidase</td><td>58</td><td>45% <sup>1152</sup></td></tr><tr><td>Api g 6</td><td>nsLTP type 2</td><td>7</td><td>38%</td></tr><tr><td>Api g 7</td><td>Defensin like protein 1</td><td>12</td><td>50% <sup>1144</sup></td></tr><tr><td rowspan="3">Carrot<br>(Daucus carota)</td><td>Dau c 1</td><td>Pathogenesis related protein 10 (PR-10)</td><td>16</td><td>58-100% <sup>1153</sup></td></tr><tr><td>Dau c 4</td><td>Profilin</td><td>14</td><td>18% risk factor pollen profilin sensitisation <sup>1153</sup></td></tr><tr><td>Dau c 5</td><td>Isoflavone reductase-like protein</td><td>33</td><td>6-20% <sup>1153</sup></td></tr><tr><td colspan="5"><strong>SOLANALES</strong></td></tr><tr><td rowspan="7">Tomato<br>(Solanum<br>lycopersicum)</td><td>Sola l 1</td><td>Profilin</td><td>14</td><td>32%</td></tr><tr><td>Sola l 2</td><td>Beta-fructofuranosidase</td><td>50</td><td>4/10 patients with CCD sensitisation</td></tr><tr><td>Sola l 3</td><td>nsLTP type 1</td><td>9</td><td>Not available</td></tr><tr><td>Sola l 4</td><td>Pathogenesis-related protein, PR-10, TSI-1</td><td>20</td><td>76%; Bet v 1 sensitisation risk factor</td></tr><tr><td>Sola l 5</td><td>Cyclophilin</td><td>19</td><td>Not available</td></tr><tr><td>Sola l 6</td><td>nsLTP type 2</td><td>7</td><td>71%</td></tr><tr><td>Sola l 7</td><td>nsLTP type 1</td><td>13</td><td>71%</td></tr><tr><td rowspan="4">Potato<br>(Solanum tuberosum)<br>all data linked<br>to potato</td><td>Sola t 1</td><td>Patatin</td><td>43</td><td>74% in a small pediatric cohort</td></tr><tr><td>Sola t 2</td><td>Cathepsin D inhibitor PDI</td><td>21</td><td>51% in a small pediatric cohort</td></tr><tr><td>Sola t 3</td><td>Cysteine protease inhibitor</td><td>21</td><td>58% in a small pediatric cohort</td></tr><tr><td>Sola t 4</td><td>Serine protease inhibitor 7</td><td>16</td><td>67% in a small pediatric cohort</td></tr><tr><td colspan="5"><strong>LAURALES</strong></td></tr><tr><td>Avocado<br>(Persea americana)</td><td>Pers a 1</td><td>Chitinase class 1</td><td>32</td><td>75%</td></tr><tr><td colspan="5"><strong>ROSALES</strong></td></tr><tr><td rowspan="4">Indian hemp<br>(Cannabis sativa)</td><td>Can s 2</td><td>Profilin</td><td>14</td><td>16% (mixed exposure: airways and ingestion)</td></tr><tr><td>Can s 3</td><td>nsLTP type 1</td><td>9</td><td>72%</td></tr><tr><td>Can s 4</td><td>Oxygen evolving Enhancer Protein 2</td><td>27</td><td>No data published yet</td></tr><tr><td>Can s 5</td><td>PR-10 homologue</td><td>18</td><td>78% (airway exposure -BP allergy risk factor)</td></tr></tbody></table>

However, further studies are needed. The content of the psychoactive component tetrahydrocannabinol (THC) is higher in *C sativa* than in hemp. Different parts of the plant can induce allergic reactions such as hemp seeds¹¹⁷¹ used in food industry or marijuana (dried flowering tops and leaves) and hashish (dried resin), both frequently consumed drugs.¹¹⁷² Furthermore, (occupational) allergy to Cannabis has been described reviewed in.¹¹⁷³ Cannabis allergy manifestations range from cutaneous contact urticaria to anaphylaxis. The allergens described so far in *C sativa* are Can s 3,¹¹⁷⁴ a nsLTP, Can s 5,¹¹⁷⁵ a Bet v 1 homologue, the cannabis profilin Can s 2 and Can s 4.¹¹⁷⁶ In a recent study, among 25 patients with immediate symptoms on

exposure to cannabis, 52% were sensitized to Can s 3, 80% to Can s 5 and 16% to Can s 2.¹¹⁷⁵ Only 7% of patients with a Cannabis allergy were sensitized to Can s 4 in another study.¹¹⁷⁶ The nsLTP, Can s 3, is suspected to be the major cross-reacting allergen in the so called cannabis-food syndrome. In patients with cannabis-induced anaphylaxis, Can s 3 was the major allergen and 72% reported to suffer from a systemic food allergy, in part co-factor mediated.¹¹⁷⁰

### Clinical diagnosis of fruit and vegetable allergies

Allergies to fruits and vegetables are often initiated by a primary sensitization to pollen. Since the majority of fruit and vegetable allergens belong to a few protein families and are characterized by a
<figure><img src="image_214.png" /><figcaption>FIGURE 102 Diagnostic work-up in Rosaceae fruit allergy. * Patients with sensitization to birch pollen or other Fagales tree pollen and history of Rosaceae fruit induced oropharyngeal symptoms usually do not need further investigation; + Sensitivity of skin test or *in vitro* IgE determination using fruit extracts might be low due to underrepresentation of Bet v 1 homologues; $ In patients from Mediterranean countries: OAS can also be linked to LTP or profilin sensitization. In case of LTP-mediated OAS, strict elimination of fresh and processed food is recommended.</figcaption></figure>

high cross-reactivity, the clinical relevance of sensitization needs to be often established by food challenges.

IgE binding to cross-reactive carbohydrates (CCDs) is frequently found in sera from allergic patients and points to high cross-reactivity between inhalant (e.g., grass pollen allergies) and plant food allergies.⁶⁷ These glycan epitopes are also called "classical CCDs"—N-Glycans of the MMXF3, MMF3, and MUXF3-type.¹⁷ However, the clinical relevance of this IgE-based immune response is regarded as of low clinical relevance. Some multiplex assays either offer a specific testing for CCDs in parallel or even include a CCD blocking step before testing protein specific IgE recognition (more information on CCDs is provided in chapter A10.

### Case history:

Allergies to pollen, latex, previous reaction(s) to the incriminated fruit/vegetable or fruits and vegetables from the same plant family.

Symptoms onset and course, elicitation by raw or processed food, co-factors (exercise, NSAID, alcohol etc.).

### Skin prick test (SPT):

* commercial fruit and vegetable extracts limited due to false negative results as a consequence of under-representation of Bet v 1 homologous proteins and in part also nsLTPs

* prick-prick test with the offending nonprocessed fruits and vegetables has increased sensitivity but is limited by false positive results due to irritation of the skin.

### Serum IgE testing:

* Due to the low stability of the Bet v 1 homologous proteins, these allergens are underrepresented (low sensitivity) in some but not all diagnostic food extracts, leading to false negative test results.
<figure><img src="image_214.png" /><figcaption>FIGURE 102 Diagnostic work-up in Rosaceae fruit allergy. * Patients with sensitization to birch pollen or other Fagales tree pollen and history of Rosaceae fruit induced oropharyngeal symptoms usually do not need further investigation; + Sensitivity of skin test or *in vitro* IgE determination using fruit extracts might be low due to underrepresentation of Bet v 1 homologues; $ In patients from Mediterranean countries: OAS can also be linked to LTP or profilin sensitization. In case of LTP-mediated OAS, strict elimination of fresh and processed food is recommended.</figcaption></figure>

high cross-reactivity, the clinical relevance of sensitization needs to be often established by food challenges.

IgE binding to cross-reactive carbohydrates (CCDs) is frequently found in sera from allergic patients and points to high cross-reactivity between inhalant (e.g., grass pollen allergies) and plant food allergies.⁶⁷ These glycan epitopes are also called "classical CCDs"—N-Glycans of the MMXF3, MMF3, and MUXF3-type.¹⁷ However, the clinical relevance of this IgE-based immune response is regarded as of low clinical relevance. Some multiplex assays either offer a specific testing for CCDs in parallel or even include a CCD blocking step before testing protein specific IgE recognition (more information on CCDs is provided in chapter A10.

### Case history:

Allergies to pollen, latex, previous reaction(s) to the incriminated fruit/vegetable or fruits and vegetables from the same plant family.

Symptoms onset and course, elicitation by raw or processed food, co-factors (exercise, NSAID, alcohol etc.).

### Skin prick test (SPT):

* commercial fruit and vegetable extracts limited due to false negative results as a consequence of under-representation of Bet v 1 homologous proteins and in part also nsLTPs

* prick-prick test with the offending nonprocessed fruits and vegetables has increased sensitivity but is limited by false positive results due to irritation of the skin.

### Serum IgE testing:

* Due to the low stability of the Bet v 1 homologous proteins, these allergens are underrepresented (low sensitivity) in some but not all diagnostic food extracts, leading to false negative test results.
* IgE to Bet v 1 or Bet v 1 homologous proteins in reaction pattern A (Pru p 1, Mal d 1, Act d 8, Api g 1, Dau c 1) is indicative of a Bet v 1-related fruit/vegetable allergy but limited by low specificity.

* IgE to nsLTP (Pru p 3, Mal d 3) in reaction pattern B, might be associated with systemic reactions, limited by low specificity.

* IgE to Act d 1 is a risk factor for monosensitization and for systemic reactions to kiwifruit.

* IgE to Hev b 6.02 and Hev b 11 hint to possible latex induced fruit allergy.

### Challenge tests:

* **A/C:** often not indicated if symptoms are limited to the oropharyngeal area, challenge with processed foods indicated in case of "unclear" history in terms of tolerance, i.e., in celeriac allergy.

* **B/D/E/F:** titrated challenge indicated in cases where allergy is not supported by clear-cut case history.

### Clinical management

#### Recommendations

* **A/C:** Avoidance of symptom-eliciting raw fruits and raw vegetables; avoidance of processed foods only in patients with positive oral challenges with the respective processed food

* **B/D/E/F:** Avoidance of symptom-eliciting raw and processed fruits and vegetables, for celeriac allergy also traces.

#### Pharmacotherapy (emergency kit)

* **A/C:** Due to the small risk of systemic reactions or severe local reactions (angioedema lips, swelling oral mucosa) emergency medication for p.o. self-administration (antihistamines, eventually steroids).

* **B/D/E/F:** Emergency medication for p.o. self-administration (antihistamines, steroids), and in case of systemic reaction, epinephrine for self-administration (autoinjector).

#### Allergen-specific immunotherapy

Immunotherapy with birch pollen extract in Bet v 1-mediated fruit allergy showed contradictory results.¹¹⁷,¹¹⁷ Sublingual immunotherapy with rMal d 1 provided promising results for apple allergic patients in a first small trial.²²³ Recently a trial with Bet v 1-specific monoclonal antibody provided first positive results for birch pollen allergy, while data on BP-related food allergies are not available for this approach.¹¹⁷⁹

Oral tolerance induction using raw apples was observed in Bet v 1-related apple allergy,¹¹⁸⁰ but results need to be confirmed. Sublingual immunotherapy for patients with nsLTP-induced peach allergy using a Pru p 3 quantified peach extract has shown promising results.⁴⁰¹ In another study peach and peanut allergic patients were treated with the Pru p 3 enriched peach extract and showed reduced SPT reactivity and increased threshold levels in oral challenges for peach and also peanut in the peanut allergic group after 12 months of treatment.¹¹⁸¹

## 5 - Clinical cases

### Case 1

**History:** 28 year old female patient, with recurrent anaphylactic reactions after unprocessed fruits. First anaphylaxis at the age of 4 years after ingestion of a plum, in the following after an apple, and at the age of 9 years after a peach.

**Microarrayed specific IgE (ISU-E):**

Bet v 1 undetectable; Bet v 2 - 1.2; Ara h 9 - 2.9; Cor a 8 - 3.6; Jug r 3 - 8.8; Pru p 3 -12.0.

**Diagnosis:** LTP syndrome with recurrent anaphylactic reactions after plum, peach, apple

**Recommendation:** strict elimination of symptom inducing fruits in raw and processed form. Emergency kit with antihistamines, steroids and adrenaline pen. (SLIT with Pru p 3 quantified extract has been considered but denied by the patient).

### Case 2

**History:** Male, 48 years old. Rhinoconjunctivitis to birch pollen and oropharyngeal itch to raw apples since school age. Regular ingestion of raw apples despite oral symptoms. He gets up in the night 3 am, ingests three apples on an empty stomach and develops oral itching, slight swelling of the lips and collapses. Two weeks later he gets up again in the night, ingests several apples on an empty stomach, develops severe itching of the oral mucosa, swelling of the lips and loses consciousness for few minutes. After 1 hour, recovers spontaneously.

**In-vitro testing for specific IgE [kU/l]:** Bet v 1: 88; Bet v 2 < 0.35; Pru p 3 < 0.35

**SPT:** Birch pollen extract, raw apple strongly positive

**Oral food challenge:** No symptoms with cooked apple puree, contact urticaria with blisters of the oral mucosa and slight angioedema of the lips after one quarter of a raw apple

**Diagnosis:** Anaphylactic reaction with oral contact urticaria, angioedema of lips and collapse after ingestion of large amount of raw apples on an empty stomach due to Bet v 1-related apple allergy.

**Recommendations:** Strict avoidance of raw apples; cooked apples without dietary restriction (due to thermal instability of Bet v 1-related allergens).

### Case 3

**History:** 23 years-old female, no atopic background. Ingestion of kiwifruit, after 15 minutes nausea, abdominal cramps, emesis, diarrhea, drop of blood pressure. Emergency treatment.

**SPT:** negative to birch and grass pollen extract, latex, isolated positive skin test with raw kiwifruit.

**In-vitro testing specific IgE [kU/l] (ImmunoCAP Specific IgE test):** Bet v 1 < 0.35; Bet v 2<0.35; latex < 0.35; kiwi extract < 0.35.

**Microarrayed specific IgE:** positive to Act d 1 and Act d 2 Oral challenge: mucosa challenge with kiwifruit: oral contact urticaria, flushed face and nausea.

**Diagnosis:** primary kiwi allergy with sensitization to Act d 1 and Act d 2.

**Recommendations:** strict elimination diet for raw and processed kiwifruit, emergency kit with antihistamines, steroids and adrenaline pen.
* IgE to Bet v 1 or Bet v 1 homologous proteins in reaction pattern A (Pru p 1, Mal d 1, Act d 8, Api g 1, Dau c 1) is indicative of a Bet v 1-related fruit/vegetable allergy but limited by low specificity.

* IgE to nsLTP (Pru p 3, Mal d 3) in reaction pattern B, might be associated with systemic reactions, limited by low specificity.

* IgE to Act d 1 is a risk factor for monosensitization and for systemic reactions to kiwifruit.

* IgE to Hev b 6.02 and Hev b 11 hint to possible latex induced fruit allergy.

### Challenge tests:

* **A/C:** often not indicated if symptoms are limited to the oropharyngeal area, challenge with processed foods indicated in case of "unclear" history in terms of tolerance, i.e., in celeriac allergy.

* **B/D/E/F:** titrated challenge indicated in cases where allergy is not supported by clear-cut case history.

### Clinical management

#### Recommendations

* **A/C:** Avoidance of symptom-eliciting raw fruits and raw vegetables; avoidance of processed foods only in patients with positive oral challenges with the respective processed food

* **B/D/E/F:** Avoidance of symptom-eliciting raw and processed fruits and vegetables, for celeriac allergy also traces.

#### Pharmacotherapy (emergency kit)

* **A/C:** Due to the small risk of systemic reactions or severe local reactions (angioedema lips, swelling oral mucosa) emergency medication for p.o. self-administration (antihistamines, eventually steroids).

* **B/D/E/F:** Emergency medication for p.o. self-administration (antihistamines, steroids), and in case of systemic reaction, epinephrine for self-administration (autoinjector).

#### Allergen-specific immunotherapy

Immunotherapy with birch pollen extract in Bet v 1-mediated fruit allergy showed contradictory results.¹¹⁷,¹¹⁷ Sublingual immunotherapy with rMal d 1 provided promising results for apple allergic patients in a first small trial.²²³ Recently a trial with Bet v 1-specific monoclonal antibody provided first positive results for birch pollen allergy, while data on BP-related food allergies are not available for this approach.¹¹⁷⁹

Oral tolerance induction using raw apples was observed in Bet v 1-related apple allergy,¹¹⁸⁰ but results need to be confirmed. Sublingual immunotherapy for patients with nsLTP-induced peach allergy using a Pru p 3 quantified peach extract has shown promising results.⁴⁰¹ In another study peach and peanut allergic patients were treated with the Pru p 3 enriched peach extract and showed reduced SPT reactivity and increased threshold levels in oral challenges for peach and also peanut in the peanut allergic group after 12 months of treatment.¹¹⁸¹

## 5 - Clinical cases

### Case 1

**History:** 28 year old female patient, with recurrent anaphylactic reactions after unprocessed fruits. First anaphylaxis at the age of 4 years after ingestion of a plum, in the following after an apple, and at the age of 9 years after a peach.

**Microarrayed specific IgE (ISU-E):**

Bet v 1 undetectable; Bet v 2 - 1.2; Ara h 9 - 2.9; Cor a 8 - 3.6; Jug r 3 - 8.8; Pru p 3 -12.0.

**Diagnosis:** LTP syndrome with recurrent anaphylactic reactions after plum, peach, apple

**Recommendation:** strict elimination of symptom inducing fruits in raw and processed form. Emergency kit with antihistamines, steroids and adrenaline pen. (SLIT with Pru p 3 quantified extract has been considered but denied by the patient).

### Case 2

**History:** Male, 48 years old. Rhinoconjunctivitis to birch pollen and oropharyngeal itch to raw apples since school age. Regular ingestion of raw apples despite oral symptoms. He gets up in the night 3 am, ingests three apples on an empty stomach and develops oral itching, slight swelling of the lips and collapses. Two weeks later he gets up again in the night, ingests several apples on an empty stomach, develops severe itching of the oral mucosa, swelling of the lips and loses consciousness for few minutes. After 1 hour, recovers spontaneously.

**In-vitro testing for specific IgE [kU/l]:** Bet v 1: 88; Bet v 2 < 0.35; Pru p 3 < 0.35

**SPT:** Birch pollen extract, raw apple strongly positive

**Oral food challenge:** No symptoms with cooked apple puree, contact urticaria with blisters of the oral mucosa and slight angioedema of the lips after one quarter of a raw apple

**Diagnosis:** Anaphylactic reaction with oral contact urticaria, angioedema of lips and collapse after ingestion of large amount of raw apples on an empty stomach due to Bet v 1-related apple allergy.

**Recommendations:** Strict avoidance of raw apples; cooked apples without dietary restriction (due to thermal instability of Bet v 1-related allergens).

### Case 3

**History:** 23 years-old female, no atopic background. Ingestion of kiwifruit, after 15 minutes nausea, abdominal cramps, emesis, diarrhea, drop of blood pressure. Emergency treatment.

**SPT:** negative to birch and grass pollen extract, latex, isolated positive skin test with raw kiwifruit.

**In-vitro testing specific IgE [kU/l] (ImmunoCAP Specific IgE test):** Bet v 1 < 0.35; Bet v 2<0.35; latex < 0.35; kiwi extract < 0.35.

**Microarrayed specific IgE:** positive to Act d 1 and Act d 2 Oral challenge: mucosa challenge with kiwifruit: oral contact urticaria, flushed face and nausea.

**Diagnosis:** primary kiwi allergy with sensitization to Act d 1 and Act d 2.

**Recommendations:** strict elimination diet for raw and processed kiwifruit, emergency kit with antihistamines, steroids and adrenaline pen.
# B16 – Wheat and buckwheat allergies

Mika Mäkelä, Kati Palosuo

## Wheat allergy

### Highlights: Wheat allergy

* Wheat allergy can manifest as different clinical conditions including typical childhood food allergy, wheat-dependent, exercise-induced food allergy, and baker's allergy/asthma. The IgE response is diverse among patients and is directed against several allergens in all clinical conditions.

* Wheat is related to several clinically different allergic disorders in different organs including food allergy, wheat-dependent, exercise-induced anaphylaxis, respiratory allergy, and contact urticaria.

* Due to cross-reactivity with other allergens, including grasses, IgE measurement to whole wheat extract gives unreliable results with low specificity in diagnostics.

* There are several well-characterized allergenic molecules such as gliadins, glutenins, and alpha-amylase inhibitors, but it has been difficult to name single major allergens.

* Wheat sensitization is much more common than true clinical allergy.

* Sensitization to individual proteins is associated with disease manifestations but with significant overlap.

## 1 – The allergen sources

Wheat (*Triticum aestivum*) may be considered the most important source of food globally. For example, world trade in wheat is greater than for all other crops combined. Most food cultures serve wheat as an important part of daily meals, including bread, pasta, breakfast cereal, semolina, bulgur, and couscous, to name a few. Wheat has more vegetable protein than the other two worldwide important cereals, corn or rice. There are several different classifications of wheat and a number of different species and subspecies have been described, not to mention more than 25000 cultivars.¹¹⁸² However, there seem to be no clinically significant differences in allergenicity. In most countries, allergy to milk and egg are the two most common

food allergies, but wheat comes as third at least in Germany, Japan, and Finland.¹¹⁸³ Wheat allergy prevalence varies depending on the age and region from 0.4% to 4%.¹¹⁸³,¹¹⁸⁴ The most typical clinical manifestations of wheat-induced food allergy include IgE-mediated food allergy and celiac disease. The latter is a T-cell-mediated enteropathy induced by dietary gluten that shares features with organ-specific autoimmune disorders and it is not included in allergy treatment algorithms in most countries and is often treated by gastroenterologists rather than allergists. Therefore, celiac disease is not covered in this chapter other than in the classification as shown in Figure 103.

## 2 – Allergen families

Wheat belongs to the Triticeae tribe of the grass family Poaceae together with rye and barley. Most allergenic proteins in wheat, including the cereal prolamins and bifunctional inhibitors (alpha-amylase/trypsin inhibitors), are members of the prolamin superfamily. The cereal prolamins (gliadins and glutenins) are seed storage proteins that are found in the grains of cereal grasses (Figure 104). Wheat prolamins share a great degree of sequence and structural homology with each other and with the corresponding proteins in rye and barley.³²²

## 3 – Allergenic molecules

The measurement of wheat-specific IgE and its use for clinical diagnosis is problematic due to the low specificity when using whole-wheat extract as a test allergen either in SPTs or in serum assays. Wheat-specific IgE is common among atopic children at all ages without true food allergies—up to 65% of the patients with grass pollen allergy had false-positive IgE-ab test results to wheat extracts.¹¹⁸⁵ On the other hand, some allergens are underrepresented in whole-wheat extract-based tests due to their relative insolubility (Figure 105).

The list of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Sub-Committee lists 28 wheat allergens (www.allergen.org) (Table 49 and Figure 104 and 106). Wheat (*Triticum aestivum*) allergen numbers start with Tri a 12 (profilin) and end with Tri a 45 (Elongation factor 1 (EIF1)

<figure><img src="image_215.png" /><figcaption>FIGURE 103 Classification of wheat-related allergic diseases. Modified from 1187</figcaption></figure>
# B16 – Wheat and buckwheat allergies

Mika Mäkelä, Kati Palosuo

## Wheat allergy

### Highlights: Wheat allergy

* Wheat allergy can manifest as different clinical conditions including typical childhood food allergy, wheat-dependent, exercise-induced food allergy, and baker's allergy/asthma. The IgE response is diverse among patients and is directed against several allergens in all clinical conditions.

* Wheat is related to several clinically different allergic disorders in different organs including food allergy, wheat-dependent, exercise-induced anaphylaxis, respiratory allergy, and contact urticaria.

* Due to cross-reactivity with other allergens, including grasses, IgE measurement to whole wheat extract gives unreliable results with low specificity in diagnostics.

* There are several well-characterized allergenic molecules such as gliadins, glutenins, and alpha-amylase inhibitors, but it has been difficult to name single major allergens.

* Wheat sensitization is much more common than true clinical allergy.

* Sensitization to individual proteins is associated with disease manifestations but with significant overlap.

## 1 – The allergen sources

Wheat (*Triticum aestivum*) may be considered the most important source of food globally. For example, world trade in wheat is greater than for all other crops combined. Most food cultures serve wheat as an important part of daily meals, including bread, pasta, breakfast cereal, semolina, bulgur, and couscous, to name a few. Wheat has more vegetable protein than the other two worldwide important cereals, corn or rice. There are several different classifications of wheat and a number of different species and subspecies have been described, not to mention more than 25000 cultivars.¹¹⁸² However, there seem to be no clinically significant differences in allergenicity. In most countries, allergy to milk and egg are the two most common

food allergies, but wheat comes as third at least in Germany, Japan, and Finland.¹¹⁸³ Wheat allergy prevalence varies depending on the age and region from 0.4% to 4%.¹¹⁸³,¹¹⁸⁴ The most typical clinical manifestations of wheat-induced food allergy include IgE-mediated food allergy and celiac disease. The latter is a T-cell-mediated enteropathy induced by dietary gluten that shares features with organ-specific autoimmune disorders and it is not included in allergy treatment algorithms in most countries and is often treated by gastroenterologists rather than allergists. Therefore, celiac disease is not covered in this chapter other than in the classification as shown in Figure 103.

## 2 – Allergen families

Wheat belongs to the Triticeae tribe of the grass family Poaceae together with rye and barley. Most allergenic proteins in wheat, including the cereal prolamins and bifunctional inhibitors (alpha-amylase/trypsin inhibitors), are members of the prolamin superfamily. The cereal prolamins (gliadins and glutenins) are seed storage proteins that are found in the grains of cereal grasses (Figure 104). Wheat prolamins share a great degree of sequence and structural homology with each other and with the corresponding proteins in rye and barley.³²²

## 3 – Allergenic molecules

The measurement of wheat-specific IgE and its use for clinical diagnosis is problematic due to the low specificity when using whole-wheat extract as a test allergen either in SPTs or in serum assays. Wheat-specific IgE is common among atopic children at all ages without true food allergies—up to 65% of the patients with grass pollen allergy had false-positive IgE-ab test results to wheat extracts.¹¹⁸⁵ On the other hand, some allergens are underrepresented in whole-wheat extract-based tests due to their relative insolubility (Figure 105).

The list of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Sub-Committee lists 28 wheat allergens (www.allergen.org) (Table 49 and Figure 104 and 106). Wheat (*Triticum aestivum*) allergen numbers start with Tri a 12 (profilin) and end with Tri a 45 (Elongation factor 1 (EIF1)

<figure><img src="image_215.png" /><figcaption>FIGURE 103 Classification of wheat-related allergic diseases. Modified from 1187</figcaption></figure>
(serine protease inhibitor-like protein). Many of the not yet clinically well-studied allergens are homologous to characterized grass pollen allergens or seed allergens from related cereals. Wheat proteins have been broadly divided into water-soluble albumins, salt-soluble globulins, and insoluble prolamins, including the gliadins, which are soluble in aqueous alcohols, and the glutenins¹¹⁸¹ (Figure 105). The gliadins and glutenins are the major storage proteins in the wheat grain, also making wheat flour suitable for baking. Each of these fractions contains allergenic proteins, which have been associated with clinical symptoms, but as yet, there is no consensus definition

of major and minor allergens of wheat. Little is known also of the al-lergenicity as what comes to heating and processing of the fractions.

Sensitization to wheat among children was <1% in a systematic review taking into account a number of studies around the world¹¹⁴⁰. In a population-based study among six-year-old children in Britain, wheat sensitization rate was 0.4% and most of this was concluded to result from grass sensitization based on the food challenges.¹¹⁸² No studies have examined response to single proteins at population level.

Cross-reactivity of wheat comes at least from sensitization to grass pollen (Figure 107). It varies, however, how much of the sensitization can be explained on this at different age groups and in different disease conditions. Wheat is also highly cross-reactive with other cereals, mainly rye and barley. Oats belong to the same grass family but are more distantly related to wheat. Children with challenge-proven wheat allergy usually tolerate ingested oats despite frequent sensitization.¹¹⁸³ Early studies showed that prolamins like gamma-70 and gamma-35 secalins in rye and gamma-3 hordein in barley cross-react with omega-5 gliadin¹¹⁸⁴ and there are several other proteins among these three cereals, which are highly cross-reactive. Moreover, there is high sequence identity among many other proteins such as α-purothionins from wheat, rye, and barley (>80%).¹¹⁸⁵ In a large study of baker's allergy, rye flour inhibited binding of IgE to most wheat allergens at a significant level.¹¹⁸⁶

4 – Sensitization to individual molecules and their clinical relevance

The best characterized single wheat allergen is omega-5 gliadin (Tri a 19), which is a major allergen for wheat-dependent, exercise-induced anaphylaxis (WDEIA), later in this document clinical

<figure><img src="image_216.png" /><figcaption>FIGURE 104 Allergen families and allergen proteins in wheat</figcaption></figure>

<figure><img src="image_217.png" /><figcaption>FIGURE 105 Allergenic molecules of wheat grouped according to their solubility</figcaption></figure>
(serine protease inhibitor-like protein). Many of the not yet clinically well-studied allergens are homologous to characterized grass pollen allergens or seed allergens from related cereals. Wheat proteins have been broadly divided into water-soluble albumins, salt-soluble globulins, and insoluble prolamins, including the gliadins, which are soluble in aqueous alcohols, and the glutenins¹¹⁸¹ (Figure 105). The gliadins and glutenins are the major storage proteins in the wheat grain, also making wheat flour suitable for baking. Each of these fractions contains allergenic proteins, which have been associated with clinical symptoms, but as yet, there is no consensus definition

of major and minor allergens of wheat. Little is known also of the al-
lergenicity as what comes to heating and processing of the fractions.

Sensitization to wheat among children was <1% in a systematic review taking into account a number of studies around the world¹¹⁴⁰. In a population-based study among six-year-old children in Britain, wheat sensitization rate was 0.4% and most of this was concluded to result from grass sensitization based on the food challenges.¹¹⁸² No studies have examined response to single proteins at population level.

Cross-reactivity of wheat comes at least from sensitization to grass pollen (Figure 107). It varies, however, how much of the sensitization can be explained on this at different age groups and in different disease conditions. Wheat is also highly cross-reactive with other cereals, mainly rye and barley. Oats belong to the same grass family but are more distantly related to wheat. Children with challenge-proven wheat allergy usually tolerate ingested oats despite frequent sensitization.¹¹⁸³ Early studies showed that prolamins like gamma-70 and gamma-35 secalins in rye and gamma-3 hordein in barley cross-react with omega-5 gliadin¹¹⁸⁴ and there are several other proteins among these three cereals, which are highly cross-reactive. Moreover, there is high sequence identity among many other proteins such as α-purothionins from wheat, rye, and barley (>80%).¹¹⁸⁵ In a large study of baker's allergy, rye flour inhibited binding of IgE to most wheat allergens at a significant level.¹¹⁸⁶

4 – Sensitization to individual molecules and their
clinical relevance

The best characterized single wheat allergen is omega-5 gliadin (Tri a 19), which is a major allergen for wheat-dependent, exercise-induced anaphylaxis (WDEIA), later in this document clinical

<figure><img src="image_216.png" /><figcaption>FIGURE 104 Allergen families and allergen proteins in wheat</figcaption></figure>

<figure><img src="image_217.png" /><figcaption>FIGURE 105 Allergenic molecules of wheat grouped according to their solubility</figcaption></figure>
<table><caption>TABLE 49 Wheat allergens identified to date</caption><thead><tr><th>Allergenic Molecule</th><th>Biochemical name</th><th>Prevalence among patients (%)</th><th>Molecular weight (kDa)</th><th>Heat stability</th></tr></thead><tbody><tr><td>Tri a 12</td><td>Profilin</td><td>2.5% of patients with BA 10% of patients with BA</td><td>14</td><td>Low</td></tr><tr><td>Tri a 14</td><td>Non-specific lipid transfer protein</td><td>patients with BA</td><td>9</td><td>High</td></tr><tr><td>Tri a 15</td><td>Monomeric alpha-amylase inhibitor 0.29</td><td>41% in wheat allergy</td><td>56</td><td>High</td></tr><tr><td>Tri a 17</td><td>Beta-amylase</td><td>?</td><td>65</td><td>High in slightly acidic conditions</td></tr><tr><td>Tri a 18</td><td>Agglutinin isolectin 1</td><td>50-70% of wheat allergic patients, &gt; 80% in WDEIA</td><td>35-38</td><td>High</td></tr><tr><td>Tri a 19</td><td>Omega-5-gliadin, seed storage protein</td><td></td><td>30-45</td><td>High</td></tr><tr><td>Tri a 20</td><td>Gamma gliadin</td><td></td><td>13</td><td>Low</td></tr><tr><td>Tri a 21</td><td>Alpha-beta-gliadin</td><td>50-70% of wheat allergic patients</td><td>88</td><td></td></tr><tr><td>Tri a 25</td><td>Thioredoxin</td><td>50-70% of wheat allergic patients, 20% in WDEIA</td><td>27</td><td></td></tr><tr><td>Tri a 26</td><td>High molecular weight glutenin</td><td></td><td>13</td><td>High</td></tr><tr><td>Tri a 27</td><td>Thiol reductase homologue</td><td>50-70% of wheat allergic patients</td><td>13</td><td>High</td></tr><tr><td>Tri a 28</td><td>Dimeric alpha-amylase inhibitor 0.19</td><td>37% of wheat allergic patients</td><td>16</td><td>High</td></tr><tr><td>Tri a 29</td><td>Tetrameric alpha-amylase inhibitor CM1/CM2</td><td></td><td>26</td><td></td></tr><tr><td>Tri a 30</td><td>Tetrameric alpha-amylase inhibitor CM3</td><td></td><td>40</td><td></td></tr><tr><td>Tri a 31</td><td>Triosephosphate-isomerase</td><td></td><td>40-42</td><td></td></tr><tr><td>Tri a 32</td><td>1-cys-peroxiredoxin</td><td>60-80% of wheat allergic patients</td><td>40</td><td></td></tr><tr><td>Tri a 33</td><td>Serpin</td><td>16% of wheat allergic patients</td><td>12</td><td>High</td></tr><tr><td>Tri a 34</td><td>Glyceraldehyde-3-phosphate-dehydrogenase</td><td></td><td>15.96</td><td></td></tr><tr><td>Tri a 35</td><td>Dehydrin</td><td></td><td></td><td></td></tr><tr><td>Tri a 36</td><td>Low molecular weight glutenin GluB3-23</td><td></td><td></td><td></td></tr><tr><td>Tri a 37</td><td>Alpha purothionin</td><td></td><td></td><td></td></tr><tr><td>Tri a 39</td><td>Serine protease inhibitor-like protein</td><td></td><td></td><td></td></tr><tr><td>Tri a 40</td><td>Chloroform/methanol-soluble (CM) 17 protein [alpha-amylase inhibitor]</td><td></td><td></td><td></td></tr><tr><td>Tri a 41</td><td>Mitochondrial ubiquitin ligase activator of NFKB 1</td><td></td><td></td><td></td></tr><tr><td>Tri a 42</td><td>Hypothetical protein from cDNA</td><td></td><td></td><td></td></tr><tr><td>Tri a 43</td><td>Hypothetical protein from cDNA</td><td></td><td></td><td></td></tr><tr><td>Tri a 44</td><td>Endosperm transfer cell specific PR60 precursor</td><td></td><td></td><td></td></tr><tr><td>Tri a 45</td><td>Elongation factor 1 (EIF1)</td><td></td><td></td><td></td></tr></tbody></table>

form B. It is also an important allergen in early childhood wheat allergy with immediate onset symptoms and atopic eczema (later A type)¹¹⁸⁴,¹¹⁸⁷⁻¹¹⁸⁹ and baker's asthma/allergy (type C).¹¹⁸⁶ Other relatively well-documented allergens include alpha-amylase inhibitors (AAI), the response to which is associated with both baker's allergy and food allergy,¹¹⁸¹,¹¹⁸⁶ wheat LTP has also obvious clinical relevance and it has been associated with baker's asthma¹¹⁹⁰ and food allergy.¹¹⁹¹ So far, attempts to find single allergens predicting clinical reactivity have produced at best high sensitivity with the expense of low specificity. Although an early study showed up to 100% specificity for clinical response with sensitization to omega-5 gliadin,¹¹⁸⁷ later larger studies recruiting more heterogeneous patient groups have produced much lower rates for both sensitivity and specificity.¹¹⁸¹,¹¹⁸⁹ There are many more relevant sensitizations to single proteins other than gliadins, AAI, or LTP. Two studies demonstrated the role of sensitization to both low-molecular-weight (LMW) Tri a 36 and the high-molecular-weight (HMW) glutenin, Tri

a 26 with the most typical type of childhood wheat allergy.¹¹⁸¹,¹¹⁸⁹ Moreover, omega-5 gliadin is not the only gliadin that seems to be of significance. Also alpha-, beta-, and gamma-gliadins present as important allergens in several studies.¹¹⁸¹,¹¹⁸⁹ Recently, based on construction of *T. aestivum* cDNA library and screening it with serum IgE from patients suffering from respiratory wheat allergy five novel wheat allergens were characterized: a thioredoxin h isoform, glutathione transferase, 1-Cys-peroxiredoxin, profilin, and dehydrin. Particularly of these, a potential and emerging food allergen is alpha-purothionin Tri a 37.¹¹⁸⁵ In the largest study of any wheat-allergic patients, 19 recombinant wheat flour proteins and 2 cross-reactive carbohydrate determinants were tested in sera of 101 bakers from several European countries with wheat flour allergy. Not a single alergen emerged as a major one and each baker showed an individual IgE-binding profile with great interindividual variation.¹¹⁸⁶ Taken altogether, there is generally a significant overlap of the responses to individual proteins in different disease conditions.
<table><caption>TABLE 49 Wheat allergens identified to date</caption><thead><tr><th>Allergenic Molecule</th><th>Biochemical name</th><th>Prevalence among patients (%)</th><th>Molecular weight (kDa)</th><th>Heat stability</th></tr></thead><tbody><tr><td>Tri a 12</td><td>Profilin</td><td>2.5% of patients with BA 10% of patients with BA</td><td>14</td><td>Low</td></tr><tr><td>Tri a 14</td><td>Non-specific lipid transfer protein</td><td>patients with BA</td><td>9</td><td>High</td></tr><tr><td>Tri a 15</td><td>Monomeric alpha-amylase inhibitor 0.29</td><td>41% in wheat allergy</td><td>56</td><td>High</td></tr><tr><td>Tri a 17</td><td>Beta-amylase</td><td>?</td><td>65</td><td>High in slightly acidic conditions</td></tr><tr><td>Tri a 18</td><td>Agglutinin isolectin 1</td><td>50-70% of wheat allergic patients, &gt; 80% in WDEIA</td><td>35-38</td><td>High</td></tr><tr><td>Tri a 19</td><td>Omega-5-gliadin, seed storage protein</td><td></td><td>30-45</td><td>High</td></tr><tr><td>Tri a 20</td><td>Gamma gliadin</td><td></td><td>13</td><td>Low</td></tr><tr><td>Tri a 21</td><td>Alpha-beta-gliadin</td><td>50-70% of wheat allergic patients</td><td>88</td><td></td></tr><tr><td>Tri a 25</td><td>Thioredoxin</td><td>50-70% of wheat allergic patients, 20% in WDEIA</td><td>27</td><td></td></tr><tr><td>Tri a 26</td><td>High molecular weight glutenin</td><td></td><td>13</td><td>High</td></tr><tr><td>Tri a 27</td><td>Thiol reductase homologue</td><td>50-70% of wheat allergic patients</td><td>13</td><td>High</td></tr><tr><td>Tri a 28</td><td>Dimeric alpha-amylase inhibitor 0.19</td><td>37% of wheat allergic patients</td><td>16</td><td>High</td></tr><tr><td>Tri a 29</td><td>Tetrameric alpha-amylase inhibitor CM1/CM2</td><td></td><td>26</td><td></td></tr><tr><td>Tri a 30</td><td>Tetrameric alpha-amylase inhibitor CM3</td><td></td><td>40</td><td></td></tr><tr><td>Tri a 31</td><td>Triosephosphate-isomerase</td><td></td><td>40-42</td><td></td></tr><tr><td>Tri a 32</td><td>1-cys-peroxiredoxin</td><td>60-80% of wheat allergic patients</td><td>40</td><td></td></tr><tr><td>Tri a 33</td><td>Serpin</td><td>16% of wheat allergic patients</td><td>12</td><td>High</td></tr><tr><td>Tri a 34</td><td>Glyceraldehyde-3-phosphate-dehydrogenase</td><td></td><td>15.96</td><td></td></tr><tr><td>Tri a 35</td><td>Dehydrin</td><td></td><td></td><td></td></tr><tr><td>Tri a 36</td><td>Low molecular weight glutenin GluB3-23</td><td></td><td></td><td></td></tr><tr><td>Tri a 37</td><td>Alpha purothionin</td><td></td><td></td><td></td></tr><tr><td>Tri a 39</td><td>Serine protease inhibitor-like protein</td><td></td><td></td><td></td></tr><tr><td>Tri a 40</td><td>Chloroform/methanol-soluble (CM) 17 protein [alpha-amylase inhibitor]</td><td></td><td></td><td></td></tr><tr><td>Tri a 41</td><td>Mitochondrial ubiquitin ligase activator of NFKB 1</td><td></td><td></td><td></td></tr><tr><td>Tri a 42</td><td>Hypothetical protein from cDNA</td><td></td><td></td><td></td></tr><tr><td>Tri a 43</td><td>Hypothetical protein from cDNA</td><td></td><td></td><td></td></tr><tr><td>Tri a 44</td><td>Endosperm transfer cell specific PR60 precursor</td><td></td><td></td><td></td></tr><tr><td>Tri a 45</td><td>Elongation factor 1 (EIF1)</td><td></td><td></td><td></td></tr></tbody></table>

form B. It is also an important allergen in early childhood wheat allergy with immediate onset symptoms and atopic eczema (later A type)¹¹⁸⁴,¹¹⁸⁷⁻¹¹⁸⁹ and baker's asthma/allergy (type C).¹¹⁸⁶ Other relatively well-documented allergens include alpha-amylase inhibitors (AAI), the response to which is associated with both baker's allergy and food allergy,¹¹⁸¹,¹¹⁸⁶ wheat LTP has also obvious clinical relevance and it has been associated with baker's asthma¹¹⁹⁰ and food allergy.¹¹⁹¹ So far, attempts to find single allergens predicting clinical reactivity have produced at best high sensitivity with the expense of low specificity. Although an early study showed up to 100% specificity for clinical response with sensitization to omega-5 gliadin,¹¹⁸⁷ later larger studies recruiting more heterogeneous patient groups have produced much lower rates for both sensitivity and specificity.¹¹⁸¹,¹¹⁸⁹ There are many more relevant sensitizations to single proteins other than gliadins, AAI, or LTP. Two studies demonstrated the role of sensitization to both low-molecular-weight (LMW) Tri a 36 and the high-molecular-weight (HMW) glutenin, Tri

a 26 with the most typical type of childhood wheat allergy.¹¹⁸¹,¹¹⁸⁹ Moreover, omega-5 gliadin is not the only gliadin that seems to be of significance. Also alpha-, beta-, and gamma-gliadins present as important allergens in several studies.¹¹⁸¹,¹¹⁸⁹ Recently, based on construction of *T. aestivum* cDNA library and screening it with serum IgE from patients suffering from respiratory wheat allergy five novel wheat allergens were characterized: a thioredoxin h isoform, glutathione transferase, 1-Cys-peroxiredoxin, profilin, and dehydrin. Particularly of these, a potential and emerging food allergen is alpha-purothionin Tri a 37.¹¹⁸⁵ In the largest study of any wheat-allergic patients, 19 recombinant wheat flour proteins and 2 cross-reactive carbohydrate determinants were tested in sera of 101 bakers from several European countries with wheat flour allergy. Not a single allergen emerged as a major one and each baker showed an individual IgE-binding profile with great interindividual variation.¹¹⁸⁶ Taken altogether, there is generally a significant overlap of the responses to individual proteins in different disease conditions.
<figure><img src="image_218.png" /></figure>

<figure><img src="image_219.png" /><figcaption>Gliadin</figcaption></figure>

<figure><img src="image_220.png" /><figcaption>Glutenin</figcaption></figure>

**FIGURE 106** A.Tri a 28 0.19 alpha-amylase inhibitor B. Predicted protein structure of gliadin and glutenin. Figure edited from Rasheed et al. (RSC Adv., 2014,4, 2051-2060].

## 5 - Diagnosis of wheat allergy

Due to different routes and amounts of exposure four scenarios can prompt IgE-mediated sensitizations and clinical symptoms of immediate hypersensitivity¹¹⁷⁷ (Table 50A-D).

A. Typically, IgE-mediated form of food allergy to wheat is analogous to the symptoms seen in milk or egg allergy. Allergic individuals develop symptoms within minutes to 1-2 h after ingestion of wheat. The symptoms include urticaria, angioedema, erythema, pruritus, vomiting, abdominal pain, persistent cough, hoarse voice, wheeze, stridor, respiratory distress, nasal congestion, and, in most severe cases, anaphylaxis. These may be associated also with delayed-type symptoms, which include the worsening of atopic dermatitis, and gastrointestinal symptoms such as stomach pain and diarrhea or loose stools. Early presumably gastrointestinal or cutaneous sensitization to rather stable wheat allergens (e.g., omega-5 gliadin, HMW glutenin, LMW glutenin, alpha-amylase inhibitor) in often atopic infants is the basis of most typical IgE-mediated wheat allergy, extending often until school age and in rare cases, up to adulthood.

B. Wheat-dependent, exercise-induced anaphylaxis (WDEIA) means the appearance of severe symptoms after ingestion of wheat followed by physical exercise typically among young adults. Symptoms vary from generalized urticaria to severe anaphylactic reactions. Sensitization to omega-5 gliadin is the most specific marker for the disease, but the patients are sensitized also to several other wheat allergens. This is an important albeit a not highly prevalent form of wheat allergy.

C. Baker's allergy or asthma comes from inhalation of the wheat flour. At the moment, the test allergen with most sensitivity but low specificity is whole-wheat flour (including all allergens). The specificity of testing can be improved by component-specific analysis.

D. Contact urticaria is associated with the use of cosmetics and also sometimes together with food allergy. Hydrolysis of wheat is carried out to overcome its insolubility in cosmetics and exposure to hydrolyzed wheat protein (HWP) can cause either contact urticaria or even anaphylaxis when consuming.

**Skin prick test to wheat:** Commercial wheat extract or in-house solution employing wheat flour can be used for skin prick testing (SPT). Some authorities have claimed that this should not be used at all due to the very low specificity for all types of wheat allergy.

Specificity can be improved by additional testing to omega-5 gliadin (dissolved in ethanol, in-house preparation) or other gliadins. For clinical pattern D, hydrolyzed wheat protein should be tested. There is little experience in SPT testing for other single proteins.

**Specific IgE testing:** Whole wheat extract, Tri a 14, Tri a 19, gliadins are commercially available for determination of allergen-specific IgE. Wheat extract has low specificity and high sensitivity and can be useful in clinical patterns A–C. Omega-5 gliadin and gliadins (alpha, beta, gamma) can be useful for clinical patterns A and B. Lipid transfer proteins (Tri a 14) for A and B, probably have no cross-reactivity with grass pollen although there are not enough data to exclude this. Measuring sensitization may help in differentiating wheat sensitization from pollen allergy in patients with high levels of grass pollen-specific IgE, but this not very sensitive. AAls, particularly dimeric 0.19, LMW and HMW glutenins, Tri a 37 can be useful for clinical patterns A and C. The combination of Tri a 27, 28, 29, 39, and 32 for clinical pattern C.

**Oral food challenges:** Clinical pattern A mainly: various protocols with whole wheat can be used, for example, challenge in children with wheat flakes containing porridge or bread¹¹⁸¹. Start with a low dose (1-50 mg) of wheat-specific protein. A suitable time interval between the increasing doses should be an hour (digestion of wheat may be slower than milk and egg). Continue with semi-logarithmic progression steps up to at least 1 g of cumulative dose of wheat protein. Also, double-blind placebo-controlled protocols have been published both for children and adults.¹¹⁸¹,¹¹⁹²

Clinical patterns B and C: usually case history and IgE testing is enough for diagnosis. In uncertain cases such as in idiopathic anaphylaxis, carefully monitored exercise challenge with high readiness treatment of anaphylaxis after wheat ingestion may be considered. Some centers have used ASA or alcohol as an additional provoking factor instead of exercise.¹¹⁹³

Clinical pattern D: challenge on the skin with HWP containing cream. Of note, B and D may be seen in the same patient (Figure 108).

## 6 - Clinical management of wheat allergy

**Advice and avoidance:** Patients with severe wheat allergy should be discouraged to try different forms of wheat. There is no evidence of reduced allergenicity between different species of wheat such as spelt. Little is known of changes in allergenicity during
<figure><img src="image_218.png" /></figure>

<figure><img src="image_219.png" /><figcaption>Gliadin</figcaption></figure>

<figure><img src="image_220.png" /><figcaption>Glutenin</figcaption></figure>

FIGURE 106 A.Tri a 28 0.19 alpha-amylase inhibitor B. Predicted protein structure of gliadin and glutenin. Figure edited from Rasheed et al. (RSC Adv., 2014,4, 2051-2060].

5 – Diagnosis of wheat allergy

Due to different routes and amounts of exposure four scenarios can
prompt IgE-mediated sensitizations and clinical symptoms of imme-
diate hypersensitivity<sup>1177</sup> (Table 50A-D).

A Typically, IgE-mediated form of food allergy to wheat is analo-
gous to the symptoms seen in milk or egg allergy. Allergic individ-
uals develop symptoms within minutes to 1-2 h after ingestion of
wheat. The symptoms include urticaria, angioedema, erythema,
pruritus, vomiting, abdominal pain, persistent cough, hoarse
voice, wheeze, stridor, respiratory distress, nasal congestion,
and, in most severe cases, anaphylaxis. These may be associ-
ated also with delayed-type symptoms, which include the wors-
ening of atopic dermatitis, and gastrointestinal symptoms such
as stomach pain and diarrhea or loose stools. Early presumably
gastrointestinal or cutaneous sensitization to rather stable wheat
allergens (e.g., omega-5 gliadin, HMW glutenin, LMW glutenin,
alpha-amylase inhibitor) in often atopic infants is the basis of
most typical IgE-mediated wheat allergy, extending often until
school age and in rare cases, up to adulthood.

B Wheat-dependent, exercise-induced anaphylaxis (WDEIA) means the appearance of severe symptoms after ingestion of wheat followed by physical exercise typically among young adults. Symptoms vary from generalized urticaria to severe ana-phylactic reactions. Sensitization to omega-5 gliadin is the most specific marker for the disease, but the patients are sensitized also to several other wheat allergens. This is an important albeit a not highly prevalent form of wheat allergy.

C Baker's allergy or asthma comes from inhalation of the wheat flour. At the moment, the test allergen with most sensitivity but low specificity is whole-wheat flour (including all allergens). The specificity of testing can be improved by component-specific analysis.

D Contact urticaria is associated with the use of cosmetics and also sometimes together with food allergy. Hydrolysis of wheat is carried out to overcome its insolubility in cosmetics and exposure to hydrolyzed wheat protein (HWP) can cause either contact urticaria or even anaphylaxis when consuming.

**Skin prick test to wheat:** Commercial wheat extract or in-house solution employing wheat flour can be used for skin prick testing (SPT). Some authorities have claimed that this should not be used at all due to the very low specificity for all types of wheat allergy.

Specificity can be improved by additional testing to omega-5 gliadin (dissolved in ethanol, in-house preparation) or other gliadins. For clinical pattern D, hydrolyzed wheat protein should be tested. There is little experience in SPT testing for other single proteins.

**Specific IgE testing:** Whole wheat extract, Tri a 14, Tri a 19, gliadins are commercially available for determination of allergen-specific IgE. Wheat extract has low specificity and high sensitivity and can be useful in clinical patterns A–C. Omega-5 gliadin and gliadins (alpha, beta, gamma) can be useful for clinical patterns A and B. Lipid transfer proteins (Tri a 14) for A and B, probably have no cross-reactivity with grass pollen although there are not enough data to exclude this. Measuring sensitization may help in differentiating wheat sensitization from pollen allergy in patients with high levels of grass pollen-specific IgE, but this not very sensitive. AAls, particularly dimeric 0.19, LMW and HMW glutenins, Tri a 37 can be useful for clinical patterns A and C. The combination of Tri a 27, 28, 29, 39, and 32 for clinical pattern C.

**Oral food challenges:** Clinical pattern A mainly: various protocols with whole wheat can be used, for example, challenge in children with wheat flakes containing porridge or bread<sup>1181</sup>. Start with a low dose (1-50 mg) of wheat-specific protein. A suitable time interval between the increasing doses should be an hour (digestion of wheat may be slower than milk and egg). Continue with semi-logarithmic progression steps up to at least 1 g of cumulative dose of wheat protein. Also, double-blind placebo-controlled protocols have been published both for children and adults.<sup>1181,1192</sup>

Clinical patterns B and C: usually case history and IgE testing is enough for diagnosis. In uncertain cases such as in idiopathic anaphylaxis, carefully monitored exercise challenge with high readiness treatment of anaphylaxis after wheat ingestion may be considered. Some centers have used ASA or alcohol as an additional provoking factor instead of exercise.<sup>1193</sup>

Clinical pattern D: challenge on the skin with HWP contain-
ing cream. Of note, B and D may be seen in the same patient
(Figure 108).

6 – Clinical management of wheat allergy

**Advice and avoidance:** Patients with severe wheat allergy should be discouraged to try different forms of wheat. There is no evidence of reduced allergenicity between different species of wheat such as spelt. Little is known of changes in allergenicity during
<figure><img src="image_221.png" /><figcaption>TABLE 50 Clinical patterns of different types of wheat allergy</figcaption></figure>

<table><thead><tr><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>A</td><td>B</td><td>C</td><td>D</td></tr><tr><td>Routes of sensitisation (development of an allergen-specific IgE immune response)</td><td>Gastro-intestinal (or cutaneous) uptake of wheat proteins with subsequent or concomitant IgE-sensitisation to stable proteins</td><td>Gastro-intestinal uptake of wheat proteins with sensitisation to especially omega-5-gliadin</td><td>Inhalation of wheat flour and dust during grain processing and subsequent sensitisation to water-soluble allergens</td><td>Use of local cosmetics on the skin</td></tr><tr><td>Affected (age) group</td><td>Infants/children/rarely adults</td><td>Adults/adolescents</td><td>Exposed workers, typically bakers</td><td>Adolescents/adults</td></tr><tr><td>Wheat allergens involved</td><td>Gliadins (ω-5-gliadin) most important (?)</td><td>ω-5-gliadin, LTP (tri a 14)</td><td>Combination to Tri a 27, 28, 29, 39, 32 gives highest sensitivity and specificity</td><td>Hydrolyzed wheat protein (HWP)/gluten</td></tr><tr><td></td><td>HMW glutenins</td><td></td><td></td><td></td></tr><tr><td></td><td>LMW-glutenins</td><td></td><td></td><td></td></tr><tr><td></td><td>AAI's</td><td></td><td>Sensitisation to several other allergens including AAI's (particularly Tri a 15 and 30), Tri a 21 and 33 common</td><td></td></tr><tr><td>Allergen abundance</td><td>Several others with varying sensitisation rate</td><td></td><td>Not known</td><td>Common in cosmetics</td></tr><tr><td>Thermal stability</td><td>High</td><td>High</td><td>Low?</td><td>High?</td></tr></tbody></table>
<figure><img src="image_221.png" /><figcaption>TABLE 50 Clinical patterns of different types of wheat allergy</figcaption></figure>

<table><thead><tr><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td>A</td><td>B</td><td>C</td><td>D</td></tr><tr><td>Routes of sensitisation (development of an allergen-specific IgE immune response)</td><td>Gastro-intestinal (or cutaneous) uptake of wheat proteins with subsequent or concomitant IgE-sensitisation to stable proteins</td><td>Gastro-intestinal uptake of wheat proteins with sensitisation to especially omega-5-gliadin</td><td>Inhalation of wheat flour and dust during grain processing and subsequent sensitisation to water-soluble allergens</td><td>Use of local cosmetics on the skin</td></tr><tr><td>Affected (age) group</td><td>Infants/children/rarely adults</td><td>Adults/adolescents</td><td>Exposed workers, typically bakers</td><td>Adolescents/adults</td></tr><tr><td>Wheat allergens involved</td><td>Gliadins (ω-5-gliadin) most important (?)</td><td>ω-5-gliadin, LTP (tri a 14)</td><td>Combination to Tri a 27, 28, 29, 39, 32 gives highest sensitivity and specificity</td><td>Hydrolyzed wheat protein (HWP)/gluten</td></tr><tr><td></td><td>HMW glutenins</td><td></td><td></td><td></td></tr><tr><td></td><td>LMW-glutenins</td><td></td><td></td><td></td></tr><tr><td></td><td>AAI's</td><td></td><td>Sensitisation to several other allergens including AAI's (particularly Tri a 15 and 30), Tri a 21 and 33 common</td><td></td></tr><tr><td>Allergen abundance</td><td>Several others with varying sensitisation rate</td><td></td><td>Not known</td><td>Common in cosmetics</td></tr><tr><td>Thermal stability</td><td>High</td><td>High</td><td>Low?</td><td>High?</td></tr></tbody></table>
<table><tr><td>Digestive stability</td><td>High</td><td>High</td><td>Low?</td><td></td></tr><tr><td>Prevalence (North and Middle Europe)</td><td>High</td><td>Low</td><td>Low?</td><td>Low</td></tr><tr><td>Prevalence (Southern Europe)</td><td>Moderate</td><td>Low</td><td>Low?</td><td>Low</td></tr><tr><td>Elicitators (products)</td><td>All wheat products</td><td>Ingested wheat prior to exercise</td><td>Wheat flour and dust in the air</td><td>Hydrolyzed gluten in cosmetics such as facial soap</td></tr><tr><td>Symptoms</td><td>Quick onset (minutes to 2 h) of potentially severe systemic reactions with various symptoms of anaphylaxis: mucosal (i.e. oropharyngeal), cutaneous (urticaria, angioedema, eczema flaring), airway-related (upper and lower airways), gastrointestinal and/or cardiovascular symptoms</td><td>Quick onset urticaria, angioedema, and/or systemic symptoms of anaphylaxis</td><td>Airway symptoms (i.e. allergic rhinoconjunctivitis and asthma symptoms) within few hours of exposure</td><td>Typically urticaria after application of the cream/soap. Ingestion of foods containing deamidated gluten can cause systemic reactions including anaphylaxis</td></tr><tr><td>Additional clinical features</td><td>Atopic eczema (infants with wheat allergy), reactions after other cereals including rye and barley, rarely oats</td><td>Alcohol consumption enhances responsiveness</td><td></td><td>Usually patients do not have other types of wheat allergy</td></tr><tr><td>Medical diagnosis</td><td>Obvious and repeatable food allergic reaction to wheat (porridge, bread, pasta etc.)</td><td>Symptoms and history, sensitisation to omega-5-gliadin, in some cases challenge test</td><td>Allergic asthma and rhinoconjunctivitis due to wheat protein inhalation</td><td>Obvious contact urticaria when using HWP containing products. Patients can also develop type A food allergy.</td></tr><tr><td>Type of food allergy</td><td>Class 1</td><td>Class 1</td><td>Primary inhalant allergy</td><td>Class I</td></tr><tr><td>Avoidance</td><td>No oral intake of wheat at significant amounts (milligram levels)</td><td>No ingestion of wheat</td><td>Occupational avoidance strategies in situations of large wheat protein exposure</td><td>Ccosmetics containing HWP, in those with systemic reactions avoidance of HWP in food</td></tr><tr><td>Product declaration</td><td>Mandatory on each wheat-containing product (EU law)</td><td>Mandatory on each wheat-containing product (EU law)</td><td></td><td></td></tr><tr><td>Technical solution</td><td>No general technical solution available</td><td>No technical solutions</td><td>Dust extractor in occupational settings</td><td></td></tr></table>
<table><tr><td>Digestive stability</td><td>High</td><td>High</td><td>Low?</td><td></td></tr><tr><td>Prevalence (North and Middle Europe)</td><td>High</td><td>Low</td><td>Low?</td><td>Low</td></tr><tr><td>Prevalence (Southern Europe)</td><td>Moderate</td><td>Low</td><td>Low?</td><td>Low</td></tr><tr><td>Elicitators (products)</td><td>All wheat products</td><td>Ingested wheat prior to exercise</td><td>Wheat flour and dust in the air</td><td>Hydrolyzed gluten in cosmetics such as facial soap</td></tr><tr><td>Symptoms</td><td>Quick onset (minutes to 2 h) of potentially severe systemic reactions with various symptoms of anaphylaxis: mucosal (i.e. oropharyngeal), cutaneous (urticaria, angioedema, eczema flaring), airway-related (upper and lower airways), gastrointestinal and/or cardiovascular symptoms</td><td>Quick onset urticaria, angioedema, and/or systemic symptoms of anaphylaxis</td><td>Airway symptoms (i.e. allergic rhinoconjunctivitis and asthma symptoms) within few hours of exposure</td><td>Typically urticaria after application of the cream/soap. Ingestion of foods containing deamidated gluten can cause systemic reactions including anaphylaxis</td></tr><tr><td>Additional clinical features</td><td>Atopic eczema (infants with wheat allergy), reactions after other cereals including rye and barley, rarely oats</td><td>Alcohol consumption enhances responsiveness</td><td></td><td>Usually patients do not have other types of wheat allergy</td></tr><tr><td>Medical diagnosis</td><td>Obvious and repeatable food allergic reaction to wheat (porridge, bread, pasta etc.)</td><td>Symptoms and history, sensitisation to omega-5-gliadin, in some cases challenge test</td><td>Allergic asthma and rhinoconjunctivitis due to wheat protein inhalation</td><td>Obvious contact urticaria when using HWP containing products. Patients can also develop type A food allergy.</td></tr><tr><td>Type of food allergy</td><td>Class 1</td><td>Class 1</td><td>Primary inhalant allergy</td><td>Class I</td></tr><tr><td>Avoidance</td><td>No oral intake of wheat at significant amounts (milligram levels)</td><td>No ingestion of wheat</td><td>Occupational avoidance strategies in situations of large wheat protein exposure</td><td>Ccosmetics containing HWP, in those with systemic reactions avoidance of HWP in food</td></tr><tr><td>Product declaration</td><td>Mandatory on each wheat-containing product (EU law)</td><td>Mandatory on each wheat-containing product (EU law)</td><td></td><td></td></tr><tr><td>Technical solution</td><td>No general technical solution available</td><td>No technical solutions</td><td>Dust extractor in occupational settings</td><td></td></tr></table>
<figure><img src="image_222.png" /><figcaption>FIGURE 108 Diagnostic algorithm for wheat allergy</figcaption></figure>

processing. Below is the advice tailored to the clinical patterns previ-
ously identified

A Avoidance of all wheat-containing products, the level of avoidance can be titrated according to symptoms. Those with anaphylaxis should avoid products even with small amounts of wheat. Those with delayed symptoms and IgE negative to wheat should be encouraged to use the maximal dose not eliciting symptoms.

B Avoidance of all gluten-containing wheat especially if co-factors present

C Avoidance of inhalation of wheat containing proteins.

D Avoidance of cosmetics with hydrolyzed wheat protein.

**Pharmacotherapy for treatment of accidental reactions:** All wheat allergic patients should be prescribed treatment for acute allergic reactions and be given a detailed treatment plan. Below is the treatment adapted to the clinical patterns previously identified.

A For those with delayed reactions or mild systemic reactions, antihistamine at age-dependent dosages is enough. Because of the rapid absorption of cetirizine as compared to other antihistamines such as loratadine or desloratadine, it may be the antihistamine of choice. For those with a history of severe reactions in food challenge or after unintentional ingestion of wheat-containing products, the use of adrenaline autoinjector should be instructed carefully

B Adrenaline autoinjector.

C Symptomatic treatment as required for rhinitis/asthma.

**Allergen-specific immunotherapy:** At present, there are no commercially available products for allergen-specific immunotherapy. Clinical studies are being carried out on oral immunotherapy for clinical pattern A but, as to date, there are not enough published data to draw conclusions on the proper product to use or adequate protocols. A small case series with three patients with clinical pattern B in whom sublingual immunotherapy was conducted was published recently and individual thresholds of all patients increased after treatment.<sup>1194</sup>

7 – Prognosis of wheat allergy

The studies on the prognosis of wheat allergy have demonstrated a high rate of spontaneous resolution of the symptoms in children similar to that of milk or egg allergy.<sup>1189,1195</sup> In one study, sensitization to gliadins correlated best with persistent wheat hypersensitivity and the development of asthma in children.<sup>1189</sup> In a Japanese study, an anaphylactic reaction before the age of 3 years and high levels of wheat- or ω-5 gliadin-specific IgE increased the risk of persistent wheat allergy.<sup>1196</sup> Generally, high levels of wheat-specific IgE predict slower resolution and those with IgE-negative allergy are
<figure><img src="image_222.png" /><figcaption>FIGURE 108 Diagnostic algorithm for wheat allergy</figcaption></figure>

processing. Below is the advice tailored to the clinical patterns previ-
ously identified

A Avoidance of all wheat-containing products, the level of avoidance can be titrated according to symptoms. Those with anaphylaxis should avoid products even with small amounts of wheat. Those with delayed symptoms and IgE negative to wheat should be encouraged to use the maximal dose not eliciting symptoms.

B Avoidance of all gluten-containing wheat especially if co-factors present

C Avoidance of inhalation of wheat containing proteins.

D Avoidance of cosmetics with hydrolyzed wheat protein.

**Pharmacotherapy for treatment of accidental reactions:** All wheat allergic patients should be prescribed treatment for acute allergic reactions and be given a detailed treatment plan. Below is the treatment adapted to the clinical patterns previously identified.

A For those with delayed reactions or mild systemic reactions, antihistamine at age-dependent dosages is enough. Because of the rapid absorption of cetirizine as compared to other antihistamines such as loratadine or desloratadine, it may be the antihistamine of choice. For those with a history of severe reactions in food challenge or after unintentional ingestion of wheat-containing products, the use of adrenaline autoinjector should be instructed carefully

B Adrenaline autoinjector.

C Symptomatic treatment as required for rhinitis/asthma.

**Allergen-specific immunotherapy:** At present, there are no commercially available products for allergen-specific immunotherapy. Clinical studies are being carried out on oral immunotherapy for clinical pattern A but, as to date, there are not enough published data to draw conclusions on the proper product to use or adequate protocols. A small case series with three patients with clinical pattern B in whom sublingual immunotherapy was conducted was published recently and individual thresholds of all patients increased after treatment.<sup>1194</sup>

7 – Prognosis of wheat allergy

The studies on the prognosis of wheat allergy have demonstrated a high rate of spontaneous resolution of the symptoms in children similar to that of milk or egg allergy.<sup>1189,1195</sup> In one study, sensitization to gliadins correlated best with persistent wheat hypersensitivity and the development of asthma in children.<sup>1189</sup> In a Japanese study, an anaphylactic reaction before the age of 3 years and high levels of wheat- or ω-5 gliadin-specific IgE increased the risk of persistent wheat allergy.<sup>1196</sup> Generally, high levels of wheat-specific IgE predict slower resolution and those with IgE-negative allergy are
clinically tolerant by age three. Taken altogether, children should be challenged at certain intervals, in early childhood yearly, to test for development of tolerance. WDEIA and baker's asthma do not show spontaneous resolution.

## 8 - Clinical Cases

### Case 1

**Clinical History:** A 9-year-old boy. Atopic dermatitis since early infancy. First obvious reactions to wheat (skin flares with eczema, urticaria) soon after start of wheat at 6 months. First anaphylactic reaction to wheat at 2 years of age with generalized urticaria, bronchial obstruction, and vomiting. Strict avoidance and adrena-line autoinjector continued until now. Developed also birch allergy at 2 years of age and later other pollen sensitizations. Avoids some fresh vegetables such as cucumber, pea, nuts, and banana due to oral allergy syndrome symptoms. The family wants to know whether to continue avoiding wheat or not.

**Tests with extracts:** Wheat-specific IgE was 390 kU/l. In SPT whole-wheat extract 9 mm, omega-5 gliadin 7 mm, rye 5, barley 5, oat 0. Birch 7 mm, timothy grass 5 mm

**Tests with molecules:** Specific IgE for omega-5 gliadin 18 kU/l, timothy grass 40 kU/l, birch 100 kU/l

**Food challenge:** Wheat porridge 1 ml (=13 mg wheat protein) as a starting dose: mild tickling in the mouth, which resolves spontaneously. With doubling the dose, the boy starts vomiting, complains of nasal obstruction

**Conclusion:** Wheat allergy. Complete avoidance of wheat, adrenalin autoinjector guidance for the boy and all caretakers.

### Case 2

**Clinical History:** A 30-year-old female nurse. Generally healthy and mild pollen allergy. During the last few years, occasional urticaria which the patient has sometimes linked to wheat ingestion (bread, pasta). Occasionally urticarial appearance after brisk walk or jogging.

**Tests with extracts:** Wheat-specific IgE 20 kU/l. In SPT, whole-wheat extract 5 mm, omega-5 gliadin 7 mm, rye 3 mm, barley 3 mm, oat 0 mm.

**Tests with molecules:** Omega-5 gliadin (Tri a 19) 10 kU/l.

**Food challenge:** Large amount of pasta ingested. One hour later, a nurse-controlled free-field running test for 6 min was performed. During the last 2 min patient starts complaining severe itching and develops rapidly massive generalized urticaria, no signs of bronchial obstruction or severe gastrointestinal symptoms. Receives adrenalin, which relieves urticaria (see Figure 109 after one adrenalin injection). The urticaria starts increasing again in 15 min, and the patient receives another adrenalin shot. After this, the urticaria is resolved, and the patient feels fine.

**Conclusion:** wheat-dependent, exercise-induced urticaria. 4 h after ingestion of wheat no exercise including brisk walking.

### Case 3

**Clinical History:** A 37-year-old female cook who later studied to become pastry chef/ baker. After 2 years of working as a baker,

<figure><img src="image_223.png" /><figcaption>FIGURE 109 Severe urticaria on the whole body seen in a young woman after wheat ingestion and exercise challenge</figcaption></figure>

the patient started experiencing nasal symptoms first from rye flour and later from wheat and malt flours. No asthmatic symptoms at any time.

**Tests with extracts:** In-house immunoassay with the working place dust from wheat flour and rye flour positive. Wheat IgE 2.1 kU/l, rye 0.8 kU/l. In SPT, whole-wheat extract 0 mm as were the other cereals.

**Challenge:** Chamber challenge with wheat flour induced nasal symptoms and also increase in nasal resistance (acoustic rhinomanometry).

**Conclusion:** Occupational allergic rhinitis due to wheat and rye (baker's allergy). Primarily a respiration filter and change of the station in the kitchen. This did not help this patient enough, so she is considering to learn a new profession.

## 9 - Research and future perspectives

Clinically irrelevant sensitization to wheat is common and the diagnostic accuracy of wheat protein extracts is unsatisfactory. At present, there are three commercially available allergens for diagnostic purposes: gliadin (including purified α, β, γ, and ω-gliadins) Tri a 14 and Tri a 19. In addition, the ImmunoCAP ISAC contains purified alpha-amylase/trypsin inhibitor (nTri a aA_TI). However, no single allergen can be used for molecular allergy diagnostics, since the IgE response in wheat allergy is heterogeneous and directed against multiple allergens.

Detailed knowledge on the structure and immunologic properties of clinically relevant wheat allergens is needed to develop accurate diagnostic tools for wheat allergy. The complex protein structure of wheat gliadins and glutenins and their insolubility in aqueous solutions has, however, posed challenges on protein purification and structural analysis. Identification and characterization of clinically relevant IgE-binding epitopes in different forms of wheat allergy could possibly improve the accuracy of molecular allergy diagnostics.
clinically tolerant by age three. Taken altogether, children should be challenged at certain intervals, in early childhood yearly, to test for development of tolerance. WDEIA and baker's asthma do not show spontaneous resolution.

## 8 - Clinical Cases

### Case 1

**Clinical History:** A 9-year-old boy. Atopic dermatitis since early infancy. First obvious reactions to wheat (skin flares with eczema, urticaria) soon after start of wheat at 6 months. First anaphylactic reaction to wheat at 2 years of age with generalized urticaria, bronchial obstruction, and vomiting. Strict avoidance and adrena-line autoinjector continued until now. Developed also birch allergy at 2 years of age and later other pollen sensitizations. Avoids some fresh vegetables such as cucumber, pea, nuts, and banana due to oral allergy syndrome symptoms. The family wants to know whether to continue avoiding wheat or not.

**Tests with extracts:** Wheat-specific IgE was 390 kU/l. In SPT whole-wheat extract 9 mm, omega-5 gliadin 7 mm, rye 5, barley 5, oat 0. Birch 7 mm, timothy grass 5 mm

**Tests with molecules:** Specific IgE for omega-5 gliadin 18 kU/l, timothy grass 40 kU/l, birch 100 kU/l

**Food challenge:** Wheat porridge 1 ml (=13 mg wheat protein) as a starting dose: mild tickling in the mouth, which resolves spontaneously. With doubling the dose, the boy starts vomiting, complains of nasal obstruction

**Conclusion:** Wheat allergy. Complete avoidance of wheat, adrenalin autoinjector guidance for the boy and all caretakers.

### Case 2

**Clinical History:** A 30-year-old female nurse. Generally healthy and mild pollen allergy. During the last few years, occasional urticaria which the patient has sometimes linked to wheat ingestion (bread, pasta). Occasionally urticarial appearance after brisk walk or jogging.

**Tests with extracts:** Wheat-specific IgE 20 kU/l. In SPT, whole-wheat extract 5 mm, omega-5 gliadin 7 mm, rye 3 mm, barley 3 mm, oat 0 mm.

**Tests with molecules:** Omega-5 gliadin (Tri a 19) 10 kU/l.

**Food challenge:** Large amount of pasta ingested. One hour later, a nurse-controlled free-field running test for 6 min was performed. During the last 2 min patient starts complaining severe itching and develops rapidly massive generalized urticaria, no signs of bronchial obstruction or severe gastrointestinal symptoms. Receives adrenalin, which relieves urticaria (see Figure 109 after one adrenalin injection). The urticaria starts increasing again in 15 min, and the patient receives another adrenalin shot. After this, the urticaria is resolved, and the patient feels fine.

**Conclusion:** wheat-dependent, exercise-induced urticaria. 4 h after ingestion of wheat no exercise including brisk walking.

### Case 3

**Clinical History:** A 37-year-old female cook who later studied to become pastry chef/ baker. After 2 years of working as a baker,

<figure><img src="image_223.png" /><figcaption>FIGURE 109 Severe urticaria on the whole body seen in a young woman after wheat ingestion and exercise challenge</figcaption></figure>

the patient started experiencing nasal symptoms first from rye flour and later from wheat and malt flours. No asthmatic symptoms at any time.

**Tests with extracts:** In-house immunoassay with the working place dust from wheat flour and rye flour positive. Wheat IgE 2.1 kU/l, rye 0.8 kU/l. In SPT, whole-wheat extract 0 mm as were the other cereals.

**Challenge:** Chamber challenge with wheat flour induced nasal symptoms and also increase in nasal resistance (acoustic rhinomanometry).

**Conclusion:** Occupational allergic rhinitis due to wheat and rye (baker's allergy). Primarily a respiration filter and change of the station in the kitchen. This did not help this patient enough, so she is considering to learn a new profession.

## 9 - Research and future perspectives

Clinically irrelevant sensitization to wheat is common and the diagnostic accuracy of wheat protein extracts is unsatisfactory. At present, there are three commercially available allergens for diagnostic purposes: gliadin (including purified α, β, γ, and ω-gliadins) Tri a 14 and Tri a 19. In addition, the ImmunoCAP ISAC contains purified alpha-amylase/trypsin inhibitor (nTri a aA_TI). However, no single allergen can be used for molecular allergy diagnostics, since the IgE response in wheat allergy is heterogeneous and directed against multiple allergens.

Detailed knowledge on the structure and immunologic properties of clinically relevant wheat allergens is needed to develop accurate diagnostic tools for wheat allergy. The complex protein structure of wheat gliadins and glutenins and their insolubility in aqueous solutions has, however, posed challenges on protein purification and structural analysis. Identification and characterization of clinically relevant IgE-binding epitopes in different forms of wheat allergy could possibly improve the accuracy of molecular allergy diagnostics.
# Buckwheat allergy

## Highlights: Buckwheat allergy

* Allergic reactions to buckwheat may occur after ingestion, inhalation, or when handling buckwheat.

* Clinically irrelevant sensitization to buckwheat is common and the diagnostic performance of IgE to buckwheat extract and skin prick tests is low. Although buckwheat allergy is relatively infrequent, it can often cause anaphylactic reactions. IgE to Fag e 2 is associated with severe reactions, but well-defined commercially available buckwheat allergens for molecular allergy diagnostics are lacking.

* The popularity of buckwheat as a healthy, gluten-free food has increased in the European countries and USA. Buckwheat is often consumed as a hidden food allergen. Remember the possibility of buckwheat allergy when investigating unclear anaphylaxis, especially in patients on a gluten-free diet.

## 1 – The allergen sources

Two buckwheat species, originating from China, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tartaricum) are cultivated globally for food production. This chapter focuses on common buckwheat, which is the dominant species. It is widely consumed in Asia and Russia with increasing popularity in western countries, because of its high nutritional value and suitability for individuals with gluten-related disorders¹¹⁹⁷ [25, 26]. Buckwheat can be consumed as groats, and buckwheat flour is used in many foods such as noodles, bread, pastry, pancakes, blinis, and porridge. Buckwheat is often present as a hidden food allergen since there is no regulation on allergen labeling for buckwheat apart from Japan and Korea.¹¹⁹⁸ Buckwheat husks are used for pillow fillings and common buckwheat is added to animal feed.¹¹⁹⁹

Allergic reactions to buckwheat may occur after oral ingestion, inhalant exposure when producing or handling buckwheat, or when sleeping on buckwheat husk pillows. The symptoms include typical food allergy symptoms affecting the skin, gastrointestinal tract, and respiratory system as well as severe systemic reactions including anaphylaxis.¹¹⁹⁹ Allergic rhinitis, asthma, and contact urticaria have been described in the occupational setting.¹²⁰⁰

## 2 – Allergen families

Buckwheat is a pseudocereal that belongs to the Polygonaceae family. It is a grain-like seed, which shares similarities with cereal grains. Allergenic proteins in buckwheat are mainly seed storage proteins (2S albumins, 7S globulins, and 11S globulins), which belong to the prolamin and cupin superfamilies.¹²⁰¹ Taxonomically buckwheat is unrelated to wheat.

## 3 – Allergenic molecules

Several buckwheat allergens have been identified and characterized (Figure 110 and Table 51).¹²⁰² The World Health Organization/International Union of Immunological Societies Allergen Nomenclature Sub-Committee lists five common buckwheat allergens named Fag e 1 to 5 and two tartary buckwheat allergens named Fag t 1 and Fag t 2. (http://www.allergen.org/) Buckwheat allergy has been reported mainly in Asia with an estimated prevalence of 0.1% in Korea and 0.22% in Japan where it is the sixth most common cause of food allergy.¹¹⁹⁹ In Japan, buckwheat causes approximately 3% of all reported anaphylactic events to foods,¹²⁰³ and in a study including school-aged children more than half presented with anaphylaxis.¹²⁰⁴ The prevalence of buckwheat allergy may be higher in certain subgroups, for example, in patients with coeliac disease. Sensitization rates to buckwheat in the European countries and the United States vary from 1% to 9.7%, but the prevalence of true buckwheat allergy is unknown.¹¹⁹⁹,¹²⁰⁵

## 4 – Sensitization to individual molecules and their clinical relevance

Studies have focused on common buckwheat where Fag e 1, 2, and 3 are considered the major allergens. Fag e 1 is the β-subunit of 13S globulin (legumin), which in early studies was recognized by all patients with buckwheat allergy.¹²⁰⁶ Later studies showed higher diagnostic performance for the full-length protein, when comparing the purified native full-length legumin and its subunit designated as

<figure><img src="image_224.png" /><figcaption>FIGURE 110 Allergen families and allergen proteins in buckwheat</figcaption></figure>
# Buckwheat allergy

## Highlights: Buckwheat allergy

* Allergic reactions to buckwheat may occur after ingestion, inhalation, or when handling buckwheat.

* Clinically irrelevant sensitization to buckwheat is common and the diagnostic performance of IgE to buckwheat extract and skin prick tests is low. Although buckwheat allergy is relatively infrequent, it can often cause anaphylactic reactions. IgE to Fag e 2 is associated with severe reactions, but well-defined commercially available buckwheat allergens for molecular allergy diagnostics are lacking.

* The popularity of buckwheat as a healthy, gluten-free food has increased in the European countries and USA. Buckwheat is often consumed as a hidden food allergen. Remember the possibility of buckwheat allergy when investigating unclear anaphylaxis, especially in patients on a gluten-free diet.

## 1 – The allergen sources

Two buckwheat species, originating from China, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tartaricum) are cultivated globally for food production. This chapter focuses on common buckwheat, which is the dominant species. It is widely consumed in Asia and Russia with increasing popularity in western countries, because of its high nutritional value and suitability for individuals with gluten-related disorders¹¹⁹⁷ [25, 26]. Buckwheat can be consumed as groats, and buckwheat flour is used in many foods such as noodles, bread, pastry, pancakes, blinis, and porridge. Buckwheat is often present as a hidden food allergen since there is no regulation on allergen labeling for buckwheat apart from Japan and Korea.¹¹⁹⁸ Buckwheat husks are used for pillow fillings and common buckwheat is added to animal feed.¹¹⁹⁹

Allergic reactions to buckwheat may occur after oral ingestion, inhalant exposure when producing or handling buckwheat, or when sleeping on buckwheat husk pillows. The symptoms include typical food allergy symptoms affecting the skin, gastrointestinal tract, and respiratory system as well as severe systemic reactions including anaphylaxis.¹¹⁹⁹ Allergic rhinitis, asthma, and contact urticaria have been described in the occupational setting.¹²⁰⁰

## 2 – Allergen families

Buckwheat is a pseudocereal that belongs to the Polygonaceae family. It is a grain-like seed, which shares similarities with cereal grains. Allergenic proteins in buckwheat are mainly seed storage proteins (2S albumins, 7S globulins, and 11S globulins), which belong to the prolamin and cupin superfamilies.¹²⁰¹ Taxonomically buckwheat is unrelated to wheat.

## 3 – Allergenic molecules

Several buckwheat allergens have been identified and characterized (Figure 110 and Table 51).¹²⁰² The World Health Organization/International Union of Immunological Societies Allergen Nomenclature Sub-Committee lists five common buckwheat allergens named Fag e 1 to 5 and two tartary buckwheat allergens named Fag t 1 and Fag t 2. (http://www.allergen.org/) Buckwheat allergy has been reported mainly in Asia with an estimated prevalence of 0.1% in Korea and 0.22% in Japan where it is the sixth most common cause of food allergy.¹¹⁹⁹ In Japan, buckwheat causes approximately 3% of all reported anaphylactic events to foods,¹²⁰³ and in a study including school-aged children more than half presented with anaphylaxis.¹²⁰⁴ The prevalence of buckwheat allergy may be higher in certain subgroups, for example, in patients with coeliac disease. Sensitization rates to buckwheat in the European countries and the United States vary from 1% to 9.7%, but the prevalence of true buckwheat allergy is unknown.¹¹⁹⁹,¹²⁰⁵

## 4 – Sensitization to individual molecules and their clinical relevance

Studies have focused on common buckwheat where Fag e 1, 2, and 3 are considered the major allergens. Fag e 1 is the β-subunit of 13S globulin (legumin), which in early studies was recognized by all patients with buckwheat allergy.¹²⁰⁶ Later studies showed higher diagnostic performance for the full-length protein, when comparing the purified native full-length legumin and its subunit designated as

<figure><img src="image_224.png" /><figcaption>FIGURE 110 Allergen families and allergen proteins in buckwheat</figcaption></figure>
<table><caption>TABLE 51 Buckwheat allergens described to date</caption><thead><tr><th>Allergenic Molecule</th><th>Biochemical name</th><th>Prevalence among patients (%)</th><th>Molecular weight (kDa)</th><th>Heat stability</th></tr></thead><tbody><tr><td>Fag e 1</td><td>13S globulin / legumin</td><td>?</td><td>22</td><td></td></tr><tr><td>Fag e 2</td><td>2S albumin</td><td>76-87</td><td>16</td><td>High</td></tr><tr><td>Fag e 3</td><td>7S globulin / vicilin-like</td><td>83</td><td>19 (fragment)</td><td></td></tr><tr><td>Fag e 4</td><td>Antimicrobial Peptide</td><td>71</td><td>3.9</td><td></td></tr><tr><td>Fag e 5</td><td>Vicilin-like protein</td><td></td><td>55</td><td></td></tr><tr><td>Fag t 2</td><td>2S albumin</td><td>38</td><td>16</td><td>High</td></tr><tr><td>Fag t 6</td><td>Oleosin</td><td>60</td><td>18</td><td></td></tr></tbody></table>

Fag e 1. This suggests that not all relevant IgE-binding epitopes are present in the legumin subunit Fag e 1.¹²⁰⁷

Fag e 2 is a highly stable 2S albumin that is resistant to pepsin digestion in contrast to Fag e 1 and Fag e 3. Sensitization to Fag e 2 is often related with severe reactions including anaphylaxis and it is thus considered an important allergen in buckwheat anaphylaxis.¹²¹³⁻¹²¹⁵ In a small Danish cohort, including 11 patients with severe buckwheat allergy Fag e 2 on ImmunoCAP ISAC showed a relatively high specificity (96%) but low sensitivity (43%). In ELISA, the diagnostic specificity of Fag e 2 was 85% and sensitivity 100%.¹²¹²

Fag e 3 is a 7S globulin, which is the N-terminal fragment of a vicilin-like protein. Fag e 3 has weak homology to the vicilin-like allergens of cashew (Ana o 1), English walnut (Jug r 2), and 7 S globulin from sesame seed. Studies from Japan have reported Fag e 3 as the most specific allergen for the diagnosis of patients with clinical symptoms of buckwheat allergy.¹²⁰⁷ Fag e 3 had a higher diagnostic performance at the optimal cutoff than buckwheat extract and had the best clinical performance among the buckwheat allergens studied. In a group of 60 Japanese children sensitized to buckwheat, Fag e 3 predicted oral food challenge results as well as anaphylaxis.¹²⁰⁹ Two recently described allergens include Fag e 4, a hevein-like antimicrobial peptide that is potentially cross-reactive with latex, and Fag e 5, a partial peptide of a vicilin-like protein.¹²¹² In the Danish cohort of 11 buckwheat allergic patients and 41 sensitized nonallergic patients, concomitant sensitization to Fag e 1, Fag e 2, and Fag e 5, was the best predictor of clinical buckwheat allergy. Interestingly, in this population, sensitization to Fag e 3 was not observed.¹²¹²

## 5 – Diagnosis of buckwheat allergy

The diagnosis of buckwheat allergy begins with a careful assessment of clinical history (Figure 111). In suspected buckwheat allergy, sensitization can be screened by skin prick testing or the measurement of buckwheat-specific IgE. Despite high sensitivity, the specificity of these tests is rather low, and clinically irrelevant sensitization to buckwheat is common. Thus far, the only commercially available allergen component for molecular allergy diagnostics is Fag e 2 in the

ImmunoCAP ISAC microarray. Sensitization to buckwheat extract and Fag e 2 together with a positive clinical history increases the probability of buckwheat allergy. The absence of sensitization to Fag e 2, however, does not rule out clinical reactivity, because in many cases other buckwheat allergens (e.g., Fag e 1, 3, and 5) are involved. The diagnosis should thus be confirmed by an oral food challenge unless there is a recent history of a severe reaction to buckwheat.

## 6 – Clinical case

**Clinical History:** a 3-year-old boy with atopic eczema since infancy, which required daily treatment with emollients and periodic topical corticosteroids. He had experienced recurrent episodes of wheezing during respiratory infections and used regular controller treatment for asthma. His diet was unrestricted until 2 years of age, after which his parents started a gluten-free diet because allergy testing revealed low sensitization to wheat (wheat-specific serum IgE 2.33 kU/L). Wheat avoidance seemed to alleviate his atopic eczema. He experienced anaphylaxis after eating a gluten-free bread containing buckwheat, rice, and corn. The symptoms started 30 minutes after ingestion: generalized urticaria, wheezing, and vomiting. He was treated at the emergency room with intramuscular adrenaline, oral antihistamines, and inhaled salbutamol.

**Tests with extracts:** The patient had positive results for buckwheat (15.7 kU/L) and wheat (6.81 kU/L) extracts. In SPT buckwheat was 7 mm, wheat 3 mm, and gliadin was negative. Specific IgE and SPT for rice and corn were negative.

**Food challenge:** An oral buckwheat challenge was not performed because of a recent anaphylactic reaction after ingestion of buckwheat. An open oral wheat challenge with a cumulative dose of 1600 mg protein was negative.

**Test with molecules:** ImmunoCAP ISAC was positive for Fag e 2 (2.9 ISU). Wheat Tri a 14, Tri a 19, and Tri a aA/ TI (alpha amylase/ trypsin inhibitor) were negative.

**Conclusion:** Buckwheat allergy presenting with anaphylaxis. Clinically irrelevant sensitization to wheat.
<table><caption>TABLE 51 Buckwheat allergens described to date</caption><thead><tr><th>Allergenic Molecule</th><th>Biochemical name</th><th>Prevalence among patients (%)</th><th>Molecular weight (kDa)</th><th>Heat stability</th></tr></thead><tbody><tr><td>Fag e 1</td><td>13S globulin / legumin</td><td>?</td><td>22</td><td></td></tr><tr><td>Fag e 2</td><td>2S albumin</td><td>76-87</td><td>16</td><td>High</td></tr><tr><td>Fag e 3</td><td>7S globulin / vicilin-like</td><td>83</td><td>19 (fragment)</td><td></td></tr><tr><td>Fag e 4</td><td>Antimicrobial Peptide</td><td>71</td><td>3.9</td><td></td></tr><tr><td>Fag e 5</td><td>Vicilin-like protein</td><td></td><td>55</td><td></td></tr><tr><td>Fag t 2</td><td>2S albumin</td><td>38</td><td>16</td><td>High</td></tr><tr><td>Fag t 6</td><td>Oleosin</td><td>60</td><td>18</td><td></td></tr></tbody></table>

Fag e 1. This suggests that not all relevant IgE-binding epitopes are present in the legumin subunit Fag e 1.¹²⁰⁷

Fag e 2 is a highly stable 2S albumin that is resistant to pepsin digestion in contrast to Fag e 1 and Fag e 3. Sensitization to Fag e 2 is often related with severe reactions including anaphylaxis and it is thus considered an important allergen in buckwheat anaphylaxis.¹²¹³⁻¹²¹⁵ In a small Danish cohort, including 11 patients with severe buckwheat allergy Fag e 2 on ImmunoCAP ISAC showed a relatively high specificity (96%) but low sensitivity (43%). In ELISA, the diagnostic specificity of Fag e 2 was 85% and sensitivity 100%.¹²¹²

Fag e 3 is a 7S globulin, which is the N-terminal fragment of a vicilin-like protein. Fag e 3 has weak homology to the vicilin-like allergens of cashew (Ana o 1), English walnut (Jug r 2), and 7 S globulin from sesame seed. Studies from Japan have reported Fag e 3 as the most specific allergen for the diagnosis of patients with clinical symptoms of buckwheat allergy.¹²⁰⁷ Fag e 3 had a higher diagnostic performance at the optimal cutoff than buckwheat extract and had the best clinical performance among the buckwheat allergens studied. In a group of 60 Japanese children sensitized to buckwheat, Fag e 3 predicted oral food challenge results as well as anaphylaxis.¹²⁰⁹ Two recently described allergens include Fag e 4, a hevein-like antimicrobial peptide that is potentially cross-reactive with latex, and Fag e 5, a partial peptide of a vicilin-like protein.¹²¹² In the Danish cohort of 11 buckwheat allergic patients and 41 sensitized nonallergic patients, concomitant sensitization to Fag e 1, Fag e 2, and Fag e 5, was the best predictor of clinical buckwheat allergy. Interestingly, in this population, sensitization to Fag e 3 was not observed.¹²¹²

## 5 – Diagnosis of buckwheat allergy

The diagnosis of buckwheat allergy begins with a careful assessment of clinical history (Figure 111). In suspected buckwheat allergy, sensitization can be screened by skin prick testing or the measurement of buckwheat-specific IgE. Despite high sensitivity, the specificity of these tests is rather low, and clinically irrelevant sensitization to buckwheat is common. Thus far, the only commercially available allergen component for molecular allergy diagnostics is Fag e 2 in the

ImmunoCAP ISAC microarray. Sensitization to buckwheat extract and Fag e 2 together with a positive clinical history increases the probability of buckwheat allergy. The absence of sensitization to Fag e 2, however, does not rule out clinical reactivity, because in many cases other buckwheat allergens (e.g., Fag e 1, 3, and 5) are involved. The diagnosis should thus be confirmed by an oral food challenge unless there is a recent history of a severe reaction to buckwheat.

## 6 – Clinical case

**Clinical History:** a 3-year-old boy with atopic eczema since infancy, which required daily treatment with emollients and periodic topical corticosteroids. He had experienced recurrent episodes of wheezing during respiratory infections and used regular controller treatment for asthma. His diet was unrestricted until 2 years of age, after which his parents started a gluten-free diet because allergy testing revealed low sensitization to wheat (wheat-specific serum IgE 2.33 kU/L). Wheat avoidance seemed to alleviate his atopic eczema. He experienced anaphylaxis after eating a gluten-free bread containing buckwheat, rice, and corn. The symptoms started 30 minutes after ingestion: generalized urticaria, wheezing, and vomiting. He was treated at the emergency room with intramuscular adrenaline, oral antihistamines, and inhaled salbutamol.

**Tests with extracts:** The patient had positive results for buckwheat (15.7 kU/L) and wheat (6.81 kU/L) extracts. In SPT buckwheat was 7 mm, wheat 3 mm, and gliadin was negative. Specific IgE and SPT for rice and corn were negative.

**Food challenge:** An oral buckwheat challenge was not performed because of a recent anaphylactic reaction after ingestion of buckwheat. An open oral wheat challenge with a cumulative dose of 1600 mg protein was negative.

**Test with molecules:** ImmunoCAP ISAC was positive for Fag e 2 (2.9 ISU). Wheat Tri a 14, Tri a 19, and Tri a aA/ TI (alpha amylase/ trypsin inhibitor) were negative.

**Conclusion:** Buckwheat allergy presenting with anaphylaxis. Clinically irrelevant sensitization to wheat.
<figure><img src="image_225.png" /><figcaption>FIGURE 111 Diagnostic algorithm for buckwheat allergy</figcaption></figure>

7 – Research and future perspectives

Buckwheat allergy is relatively infrequent but often associated with severe reactions and anaphylaxis. Although reports of buckwheat allergy are mostly from Asian countries, it is becoming an increasing problem in Europe. Buckwheat is often present as a hidden allergen in e.g., bakery products, since it does not require labeling as a food allergen in Europe. Several buckwheat allergens have been identified;

however, their clinical relevance has been studied only in a limited number of patients, and sensitization profiles display geographical variation. Well-defined buckwheat allergens available for molecular allergy diagnostics for clinicians are still lacking. To date, the only commercially available allergen is Fag e 2 on the ImmunoCAP ISAC microarray. Further studies in a larger set of patients from different geographical areas and populations are essential to develop accurate diagnostic tools for buckwheat allergy.
<figure><img src="image_225.png" /><figcaption>FIGURE 111 Diagnostic algorithm for buckwheat allergy</figcaption></figure>

7 – Research and future perspectives

Buckwheat allergy is relatively infrequent but often associated with severe reactions and anaphylaxis. Although reports of buckwheat allergy are mostly from Asian countries, it is becoming an increasing problem in Europe. Buckwheat is often present as a hidden allergen in e.g., bakery products, since it does not require labeling as a food allergen in Europe. Several buckwheat allergens have been identified;

however, their clinical relevance has been studied only in a limited number of patients, and sensitization profiles display geographical variation. Well-defined buckwheat allergens available for molecular allergy diagnostics for clinicians are still lacking. To date, the only commercially available allergen is Fag e 2 on the ImmunoCAP ISAC microarray. Further studies in a larger set of patients from different geographical areas and populations are essential to develop accurate diagnostic tools for buckwheat allergy.
# B17 - Soy allergy

Sakura Sato, Kirsten Beyer, Motohiro Ebisawa

## Highlights

* Allergic reactions to soy are caused by exposure to whole bean products, protein products, and unprocessed soybeans.

* Soy allergens can induce food allergy and inhalant (occupational) allergies.

* In areas with Fagales pollen exposure, Bet v 1-cross-reactive soy allergen, Gly m 4, induces the most common soy allergy.

* Oropharyngeal and sometimes severe reactions to Gly m 4 are limited to fresh, hardly processed soy protein containing products.

## 1 - The allergen sources

Soybeans are a legume species, which are a rich and inexpensive nutritional source used in many dishes and processed foods. They are native to East Asia and are most widely produced in the United States, followed by South America and Asia. Fat-free (defatted) soybean meal is a source of protein for many packaged meals, including textured vegetable protein and animal feed (Figure 112).

Soybeans are grouped within the “big eight” foods and are an important source of various allergens (Table 52), responsible for 90% of all allergic reactions to soy.¹²¹⁶ Allergic reactions have been described after exposure to whole bean products, protein products, and unprocessed soybeans.¹²¹⁶⁻¹²¹⁹,¹²²² Occasionally, severe allergic reactions in children have been attributed to whole bean

<figure><img src="image_226.png" /><figcaption>FIGURE 112 Soybean foods and ingredients *The protein content is minimal.</figcaption></figure>
# B17 - Soy allergy

Sakura Sato, Kirsten Beyer, Motohiro Ebisawa

## Highlights

* Allergic reactions to soy are caused by exposure to whole bean products, protein products, and unprocessed soybeans.

* Soy allergens can induce food allergy and inhalant (occupational) allergies.

* In areas with Fagales pollen exposure, Bet v 1-cross-reactive soy allergen, Gly m 4, induces the most common soy allergy.

* Oropharyngeal and sometimes severe reactions to Gly m 4 are limited to fresh, hardly processed soy protein containing products.

## 1 - The allergen sources

Soybeans are a legume species, which are a rich and inexpensive nutritional source used in many dishes and processed foods. They are native to East Asia and are most widely produced in the United States, followed by South America and Asia. Fat-free (defatted) soybean meal is a source of protein for many packaged meals, including textured vegetable protein and animal feed (Figure 112).

Soybeans are grouped within the “big eight” foods and are an important source of various allergens (Table 52), responsible for 90% of all allergic reactions to soy.¹²¹⁶ Allergic reactions have been described after exposure to whole bean products, protein products, and unprocessed soybeans.¹²¹⁶⁻¹²¹⁹,¹²²² Occasionally, severe allergic reactions in children have been attributed to whole bean

<figure><img src="image_226.png" /><figcaption>FIGURE 112 Soybean foods and ingredients *The protein content is minimal.</figcaption></figure>
products, processed soy containing foods, and some suggested soy proteins.<sup>1215,1216</sup> Birch pollen allergic individuals have recognized allergic reactions after ingestion of hardly processed dietary soy powder-containing or soy drink products.<sup>1213,1217-1219</sup> These symptoms due to IgE-related cross-reactivity are the most common type of soy allergy in regions with relevant birch pollen or alder pollen exposure.<sup>1218,1220,1221</sup> Oral symptoms are the most common, but systemic symptoms often develop after drinking soy milk.<sup>1220,1221</sup> Harbour workers and citizens in close vicinity have developed inhalant allergies caused by high exposure and inhalation of raw unprocessed soybeans during the unloading of freight ships.<sup>1225,1226,1227</sup>

## 2 – Allergen families

Soy allergens belong to diverse protein superfamilies, such as prolamin (2S albumin and lipid transfer proteins (LTPs), cupins (7S globulin and 11S globulin), profilins, and Bet v 1-like pathogenesis-related (PR)-10 proteins, among others (Table 52). They are characterized by conserved three-dimensional structures leading to broad immunochemical IgE-mediated cross-reactions among different members of the legume family or other plant foods.

## 3 – Allergenic molecules

Eight soy proteins most commonly involved in allergic reactions to soybean have been identified and officially accepted by the IUIS Allergen Nomenclature Sub-Committee (Table 52, Figure 113). Gly m 1 (nsLTP) and Gly m 2 (defensin) are associated with asthma after the inhalation of soybean dust. In a region where soybeans are loaded and handled, Gly m 1 levels were found in dust.<sup>1225</sup> Gly m 3 belongs to the profilin superfamily, and Gly m 4 belongs to the Bet v-1-like superfamily. Gly m 4 (and possibly Gly m 3) are underrepresented in diagnostic soybean extracts, leading to vast differences between extract and single allergen-based IgE results.<sup>1226</sup> In addition, the (low) presence of Gly m 4 (and Gly m 3) in soybean extracts obscures the differentiation of food reactions to stable allergens (i.e., Gly 5<sup>1222,1230</sup>, Gly m 6<sup>1232,1235</sup> and Gly m 8)<sup>1235,1232</sup> and cross-reactions to the Bet v 1-homologue in soy, as demonstrated in cohort studies with atopic children.<sup>1228</sup> Gly m 5 and Gly m 6 belong to the cupin superfamily, and Gly m 8 belongs to the prolamine superfamily. These allergens are well represented in soy extracts and are associated with severe allergic reactions to soy in children<sup>1227,1229</sup> and adults<sup>1219</sup> based on their high resistance to heat and digestive enzymes.

<table><caption>TABLE 52 Soybean allergens (Only allergens approved by WHO/IUIS; www.allergen.org, 08-09-2021)</caption><thead><tr><td>Allergen name</td><td>Protein name</td><td>Other names</td><td>Molecular weight (kDa)</td><td>Heat stability</td></tr></thead><tbody><tr><td>Gly m 1</td><td>Hydrophobic protein (Shell)</td><td>Lipid transfer protein (LTP)</td><td>7</td><td>?</td></tr><tr><td>Gly m 2</td><td>Defensin</td><td></td><td>8</td><td>Low?</td></tr><tr><td>Gly m 3</td><td>Profilin</td><td></td><td>14</td><td>Low</td></tr><tr><td>Gly m 4</td><td>Bet v 1</td><td>Pathogenesis-related protein (PR)-10</td><td>17</td><td>Low</td></tr><tr><td>Gly m 5</td><td>7S globulin</td><td>Beta-conglycinin, Vicilin</td><td>48-65</td><td>High</td></tr><tr><td>Gly m 6</td><td>11S globulin</td><td>Glycinin, Legumin</td><td>52-61</td><td>High</td></tr><tr><td>Gly m 7</td><td>Seed biotinylated protein</td><td></td><td>76.2</td><td>?</td></tr><tr><td>Gly m 8</td><td>2S albumin</td><td></td><td>28</td><td>High</td></tr></tbody></table>

<figure><img src="image_227.png" /><figcaption>FIGURE 113 Major and relevant minor allergenic molecules from soy</figcaption></figure>
products, processed soy containing foods, and some suggested soy proteins.<sup>1215,1216</sup> Birch pollen allergic individuals have recognized allergic reactions after ingestion of hardly processed dietary soy powder-containing or soy drink products.<sup>1213,1217-1219</sup> These symptoms due to IgE-related cross-reactivity are the most common type of soy allergy in regions with relevant birch pollen or alder pollen exposure.<sup>1218,1220,1221</sup> Oral symptoms are the most common, but systemic symptoms often develop after drinking soy milk.<sup>1220,1221</sup> Harbour workers and citizens in close vicinity have developed inhalant allergies caused by high exposure and inhalation of raw unprocessed soybeans during the unloading of freight ships.<sup>1225,1226,1227</sup>

## 2 – Allergen families

Soy allergens belong to diverse protein superfamilies, such as prolamin (2S albumin and lipid transfer proteins (LTPs), cupins (7S globulin and 11S globulin), profilins, and Bet v 1-like pathogenesis-related (PR)-10 proteins, among others (Table 52). They are characterized by conserved three-dimensional structures leading to broad immunochemical IgE-mediated cross-reactions among different members of the legume family or other plant foods.

## 3 – Allergenic molecules

Eight soy proteins most commonly involved in allergic reactions to soybean have been identified and officially accepted by the IUIS Allergen Nomenclature Sub-Committee (Table 52, Figure 113). Gly m 1 (nsLTP) and Gly m 2 (defensin) are associated with asthma after the inhalation of soybean dust. In a region where soybeans are loaded and handled, Gly m 1 levels were found in dust.<sup>1225</sup> Gly m 3 belongs to the profilin superfamily, and Gly m 4 belongs to the Bet v-1-like superfamily. Gly m 4 (and possibly Gly m 3) are underrepresented in diagnostic soybean extracts, leading to vast differences between extract and single allergen-based IgE results.<sup>1226</sup> In addition, the (low) presence of Gly m 4 (and Gly m 3) in soybean extracts obscures the differentiation of food reactions to stable allergens (i.e., Gly 5<sup>1222,1230</sup>, Gly m 6<sup>1232,1235</sup> and Gly m 8)<sup>1235,1232</sup> and cross-reactions to the Bet v 1-homologue in soy, as demonstrated in cohort studies with atopic children.<sup>1228</sup> Gly m 5 and Gly m 6 belong to the cupin superfamily, and Gly m 8 belongs to the prolamine superfamily. These allergens are well represented in soy extracts and are associated with severe allergic reactions to soy in children<sup>1227,1229</sup> and adults<sup>1219</sup> based on their high resistance to heat and digestive enzymes.

<table><caption>TABLE 52 Soybean allergens (Only allergens approved by WHO/IUIS; www.allergen.org, 08-09-2021)</caption><thead><tr><td>Allergen name</td><td>Protein name</td><td>Other names</td><td>Molecular weight (kDa)</td><td>Heat stability</td></tr></thead><tbody><tr><td>Gly m 1</td><td>Hydrophobic protein (Shell)</td><td>Lipid transfer protein (LTP)</td><td>7</td><td>?</td></tr><tr><td>Gly m 2</td><td>Defensin</td><td></td><td>8</td><td>Low?</td></tr><tr><td>Gly m 3</td><td>Profilin</td><td></td><td>14</td><td>Low</td></tr><tr><td>Gly m 4</td><td>Bet v 1</td><td>Pathogenesis-related protein (PR)-10</td><td>17</td><td>Low</td></tr><tr><td>Gly m 5</td><td>7S globulin</td><td>Beta-conglycinin, Vicilin</td><td>48-65</td><td>High</td></tr><tr><td>Gly m 6</td><td>11S globulin</td><td>Glycinin, Legumin</td><td>52-61</td><td>High</td></tr><tr><td>Gly m 7</td><td>Seed biotinylated protein</td><td></td><td>76.2</td><td>?</td></tr><tr><td>Gly m 8</td><td>2S albumin</td><td></td><td>28</td><td>High</td></tr></tbody></table>

<figure><img src="image_227.png" /><figcaption>FIGURE 113 Major and relevant minor allergenic molecules from soy</figcaption></figure>
## 4 – Sensitization to individual molecules and their clinical relevance

Previous sensitization rates were mainly based on skin or IgE testing of whole soybean extracts. Sensitization rates are available only for Gly m 4–6,<sup>1226</sup> while those of Gly m 1–3 and Gly m 7–8 are still lacking.

A systematic review summarized the analysis of sensitization rates in children.<sup>1215</sup> In 40 studies, the weighted prevalence of soy allergy in children was reported to be 0.27% for the general population, 0.4% and 3.1% (1.9%) for the referred population, 2.7% for IgE-sensitized children.<sup>1215</sup> IgE testing in a large cohort of German subjects aged 3–17 years revealed allergen-specific IgE to soybean extract in 6.3% of the cohort.<sup>798</sup> A similar approach in German adults revealed sensitization rates of 3.7% for soybean extract and 10.3% for soybean allergen Gly m 4.<sup>1226</sup> Sensitization rate varies according to age and region. A large allergic Mexican population was positive for soybean in different age groups, and the positivity rate was lower in young children (≤5 years) than in older children (6–17 years).<sup>1230</sup> A study in a cohort of Japanese children revealed that the sensitization rate of Gly m 5 and Gly m 6 did not change significantly between the ages of five and nine, but Gly m 4 sensitization rate was increased.<sup>1231</sup>

Notably, conclusions on primary sensitization rates are hampered by highly cross-reactive, labile soybean allergens of low abundance: the Bet v 1-homologue Gly m 4, and soybean profilin Gly m 3 (i.e., presumably in regions with high grass pollen exposure and subsequent sensitization to grass profilin).

## 5 – Clinical patterns of soy allergy

Due to the different routes and amounts of exposure, degree of soybean processing, and physicochemical properties of the involved soybean protein allergens, three distinct scenarios (Table 53A–C) can be seen in IgE-mediated sensitization and clinical symptoms of immediate hypersensitivity.

A Early, presumably epicutaneous or intestinal sensitization to rather stable allergens (i.e., Gly m 5,<sup>1219,1227</sup> Gly m 6<sup>1227,1235</sup> and Gly m 8<sup>1229,1232</sup>) in atopic individuals are the basis of subsequent severe systemic reactions after ingestion of small amounts of soy or processed soy products.<sup>1211,1212</sup> IgE sensitization could also evolve from exposure and subsequent IgE sensitization to more than one legume (i.e., peanut and soy), prompting symptoms occasionally after ingestion of peanut or other soy products. These rare reactions have mainly been described in young infants<sup>1230,1232</sup> but are seldomly reported in adults.<sup>1219,1222</sup>

B Exposure to Fagales pollen in atopic individuals developing Bet v 1-specific IgE with variable degrees of cross-reactivity to soybean PR-10 protein Gly m 4, potentially inducing mainly oral mucosal and sometimes systemic allergic symptoms after consumption

of mildly processed soy products ( soy protein powder, soy milk, etc.) in approximately 10% of birch pollen-sensitized subjects could occur.<sup>1216,1658,1659</sup> Moreover, these individuals are likely to have very high specific IgE levels to birch pollen.<sup>1213,1650,1651</sup> This type of soy allergy due to Bet v 1 cross-reactions is considered the most prevalent soy allergy in northern and middle Europe, presumably also in North America (Canada, Northern states of the US), depending on the degree of birch pollen exposure. Even in the Japanese adult population with a low prevalence of birch pollen allergy, this type of soy allergy has been observed and is associated with sensitization to Gly m 4 due to cross-reactivity to alder pollen sensitization.<sup>1221</sup> In a recent multicenter study aiming to detect risk factors for systemic reactions induced by labile food allergens, soy milk-induced systemic reactions were found to be strongly associated with hypersensitivity to PR-10 proteins, and independent of PPI ingestion. Other factors related with severe reactions were fasting and ingestion of large amounts of unprocessed foods.<sup>338</sup>

C Massive exposure to unprocessed soybeans could induce IgE-mediated sensitization to hull allergens (Gly m 1, Gly m 2) with subsequent inhalant allergies in exposed (newly or formerly nsLTP-sensitized) individuals.<sup>1222-1224,1233</sup>

## 6 – Clinical diagnosis of soy allergy

Specific questions, proper interpretation of sensitization tests (i.e., SPT and IgE), and optional food challenges help establish the diagnosis of soy allergy. The following work-up may facilitate proper diagnosis (Figure 114).

### Case history (anamnesis):

Previous reaction(s) to soy, symptoms, affected organ system(s), onset and course (progression), soy-containing food items (high-, mildly-, nonprocessed grade), co-factors (exercise, NSAID, alcohol, etc.), previous reactions after other allergen sources (i.e., peanuts or Bet v 1-related plant foods), additional (allergic) features (i.e., birch pollen allergy, LTP sensitization), and additional atopic diseases (i.e., atopic eczema, asthma). Working hypothesis: Based on soy-related clinical patterns A–C (Table 53).

### Skin prick test (SPT):

* Commercial soy extract (reasonable results in case of highly abundant allergens, i.e., seed storage proteins; limited value due to false negative responses in case of cross-reactive labile soy allergen, i.e., Gly m 4 as elicitors).

* Prick-to-prick test with offending soy product (in case of severe anaphylactic reaction, preferably titrated testing with diluted soy product or primary IgE-testing before SPT; potentially false negative, depending on the abundance and stability of the soy allergen in question (i.e., Gly m 4)).

* Prick to prick test with mildly processed soy drinks or soy powder (if Gly m 4 is suspected).
## 4 – Sensitization to individual molecules and their clinical relevance

Previous sensitization rates were mainly based on skin or IgE testing of whole soybean extracts. Sensitization rates are available only for Gly m 4–6,<sup>1226</sup> while those of Gly m 1–3 and Gly m 7–8 are still lacking.

A systematic review summarized the analysis of sensitization rates in children.<sup>1215</sup> In 40 studies, the weighted prevalence of soy allergy in children was reported to be 0.27% for the general population, 0.4% and 3.1% (1.9%) for the referred population, 2.7% for IgE-sensitized children.<sup>1215</sup> IgE testing in a large cohort of German subjects aged 3–17 years revealed allergen-specific IgE to soybean extract in 6.3% of the cohort.<sup>798</sup> A similar approach in German adults revealed sensitization rates of 3.7% for soybean extract and 10.3% for soybean allergen Gly m 4.<sup>1226</sup> Sensitization rate varies according to age and region. A large allergic Mexican population was positive for soybean in different age groups, and the positivity rate was lower in young children (≤5 years) than in older children (6–17 years).<sup>1230</sup> A study in a cohort of Japanese children revealed that the sensitization rate of Gly m 5 and Gly m 6 did not change significantly between the ages of five and nine, but Gly m 4 sensitization rate was increased.<sup>1231</sup>

Notably, conclusions on primary sensitization rates are hampered by highly cross-reactive, labile soybean allergens of low abundance: the Bet v 1-homologue Gly m 4, and soybean profilin Gly m 3 (i.e., presumably in regions with high grass pollen exposure and subsequent sensitization to grass profilin).

## 5 – Clinical patterns of soy allergy

Due to the different routes and amounts of exposure, degree of soybean processing, and physicochemical properties of the involved soybean protein allergens, three distinct scenarios (Table 53A–C) can be seen in IgE-mediated sensitization and clinical symptoms of immediate hypersensitivity.

A Early, presumably epicutaneous or intestinal sensitization to rather stable allergens (i.e., Gly m 5,<sup>1219,1227</sup> Gly m 6<sup>1227,1235</sup> and Gly m 8<sup>1229,1232</sup>) in atopic individuals are the basis of subsequent severe systemic reactions after ingestion of small amounts of soy or processed soy products.<sup>1211,1212</sup> IgE sensitization could also evolve from exposure and subsequent IgE sensitization to more than one legume (i.e., peanut and soy), prompting symptoms occasionally after ingestion of peanut or other soy products. These rare reactions have mainly been described in young infants<sup>1230,1232</sup> but are seldomly reported in adults.<sup>1219,1222</sup>

B Exposure to Fagales pollen in atopic individuals developing Bet v 1-specific IgE with variable degrees of cross-reactivity to soybean PR-10 protein Gly m 4, potentially inducing mainly oral mucosal and sometimes systemic allergic symptoms after consumption

of mildly processed soy products ( soy protein powder, soy milk, etc.) in approximately 10% of birch pollen-sensitized subjects could occur.<sup>1216,1658,1659</sup> Moreover, these individuals are likely to have very high specific IgE levels to birch pollen.<sup>1213,1650,1651</sup> This type of soy allergy due to Bet v 1 cross-reactions is considered the most prevalent soy allergy in northern and middle Europe, presumably also in North America (Canada, Northern states of the US), depending on the degree of birch pollen exposure. Even in the Japanese adult population with a low prevalence of birch pollen allergy, this type of soy allergy has been observed and is associated with sensitization to Gly m 4 due to cross-reactivity to alder pollen sensitization.<sup>1221</sup> In a recent multicenter study aiming to detect risk factors for systemic reactions induced by labile food allergens, soy milk-induced systemic reactions were found to be strongly associated with hypersensitivity to PR-10 proteins, and independent of PPI ingestion. Other factors related with severe reactions were fasting and ingestion of large amounts of unprocessed foods.<sup>338</sup>

C Massive exposure to unprocessed soybeans could induce IgE-mediated sensitization to hull allergens (Gly m 1, Gly m 2) with subsequent inhalant allergies in exposed (newly or formerly nsLTP-sensitized) individuals.<sup>1222-1224,1233</sup>

## 6 – Clinical diagnosis of soy allergy

Specific questions, proper interpretation of sensitization tests (i.e., SPT and IgE), and optional food challenges help establish the diagnosis of soy allergy. The following work-up may facilitate proper diagnosis (Figure 114).

### Case history (anamnesis):

Previous reaction(s) to soy, symptoms, affected organ system(s), onset and course (progression), soy-containing food items (high-, mildly-, nonprocessed grade), co-factors (exercise, NSAID, alcohol, etc.), previous reactions after other allergen sources (i.e., peanuts or Bet v 1-related plant foods), additional (allergic) features (i.e., birch pollen allergy, LTP sensitization), and additional atopic diseases (i.e., atopic eczema, asthma). Working hypothesis: Based on soy-related clinical patterns A–C (Table 53).

### Skin prick test (SPT):

* Commercial soy extract (reasonable results in case of highly abundant allergens, i.e., seed storage proteins; limited value due to false negative responses in case of cross-reactive labile soy allergen, i.e., Gly m 4 as elicitors).

* Prick-to-prick test with offending soy product (in case of severe anaphylactic reaction, preferably titrated testing with diluted soy product or primary IgE-testing before SPT; potentially false negative, depending on the abundance and stability of the soy allergen in question (i.e., Gly m 4)).

* Prick to prick test with mildly processed soy drinks or soy powder (if Gly m 4 is suspected).
<table><caption>TABLE 53 Features and clinical pattern of three different types of soy allergy</caption><thead><tr><th>Clinical pattern</th><th>A</th><th>B</th><th>C</th></tr></thead><tbody><tr><td>Routes of sensitisation</td><td>(1) Epicutaneous or intestinal uptake of soybean proteins with subsequent IgE-sensitisation to stable soybean proteins or (2) Epicutaneous or intestinal sensitisation of other legume proteins (i.e. peanut) with subsequent cross-reactivity to i.e. stable soybean proteins</td><td>Exposure to Fagales pollen and IgE-sensitisation due to cross reactivity to soybean proteins</td><td></td></tr><tr><td>Prevalence (North and Middle Europe)</td><td>Low</td><td>High</td><td>?</td></tr><tr><td>Prevalence (Southern Europe)</td><td>Low</td><td>Low</td><td>Occasionally asthma outbreaks in the past</td></tr><tr><td>Affected (age) group</td><td>(1) Infants/children (2) Adults</td><td>Adults/adolescents/Children</td><td>Exposed workers and citizens in close vicinity</td></tr><tr><td>Soybean allergens involved</td><td>Gly m 5, Gly m 6, Gly m 8</td><td>(1) Gly m 4 (2) Gly m 3 (presumably)</td><td>Gly m 1, Gly m 2</td></tr><tr><td>Allergen abundance</td><td>Moderate to high content (i.e. seed storage proteins Gly m 5, Gly m 6 and Gly m 8) in soy beans and related products</td><td>(1) Low content of Gly m 4 in soy beans and soy protein (0.01–0.1%) and related, less processed soy products; (2) Gly m 3 content not known</td><td>Not known</td></tr><tr><td>Thermal stability</td><td>High</td><td>Low</td><td>Moderate</td></tr><tr><td>Digestive stability</td><td>High</td><td>Low</td><td>Moderate</td></tr><tr><td>Elicitors (products)</td><td>Many soy products (including highly processed or refined soy products)</td><td>Mildly processed soy products (i.e. soy drinks, soy protein powder)</td><td>Unprocessed soybeans (i.e. during unloading)</td></tr><tr><td>Symptoms</td><td>Quick onset (minutes to 2 h) of potentially severe systemic reactions with various symptoms of anaphylaxis: mucosal (i.e. oropharyngeal), cutaneous (urticaria, angioedema, eczema flaring), airway-related (upper and lower airways), gastrointestinal and/or cardiovascular symptoms</td><td>Quick onset (2–30 min) mostly mild mucosal symptoms and/or rare systemic symptoms of anaphylaxis</td><td>Airworthy symptoms (i.e. allergic rhinoconjunctivitis and asthma symptoms) within few hours of exposure</td></tr><tr><td>Additional clinical features</td><td>Atopic eczema (i.e. in infants with soy allergy), sometimes also (potentially severe) reactions after other legumes, (i.e. peanut, lupine, seeds or tree nuts)</td><td>Commonly additional (multiple) clinical cross reactivities to other Bev v 1-related plant foods, (i.e. apple, hazelnut, cherry, plum, peach, carrot, celery)</td><td></td></tr><tr><td>Medical diagnosis</td><td>Risk of systemic allergic reaction to stable soybean proteins (Gly m 5, Gly m 6, and Gly m 8)</td><td>Fagales pollen/Bet v 1-related food allergy to cross reactive soy allergen</td><td>Allergic asthma and rhinoconjunctivitis due to soy protein inhalation</td></tr><tr><td>Avoidance</td><td>Advising avoidance of allergenic soy products, in most cases soy sauce and miso can be consumed</td><td>Gly m 4 No ingestion of large amounts of mildly processed or unprocessed soy products</td><td>Occupational avoidance strategies in situations of large soy protein exposure (unloading of soy shipments)</td></tr><tr><td>Product declaration</td><td>Mandatory on each soy containing product (EU law)</td><td>(Voluntary) additional warning on hardly processed soy products particularly for birch pollen allergic individuals</td><td></td></tr><tr><td>Technical solution</td><td>No general technical solution available</td><td>Thermic or pressure processing of soy to reduce content in labile soy proteins</td><td>Dust extractor in occupational settings</td></tr></tbody></table>
<table><caption>TABLE 53 Features and clinical pattern of three different types of soy allergy</caption><thead><tr><th>Clinical pattern</th><th>A</th><th>B</th><th>C</th></tr></thead><tbody><tr><td>Routes of sensitisation</td><td>(1) Epicutaneous or intestinal uptake of soybean proteins with subsequent IgE-sensitisation to stable soybean proteins or (2) Epicutaneous or intestinal sensitisation of other legume proteins (i.e. peanut) with subsequent cross-reactivity to i.e. stable soybean proteins</td><td>Exposure to Fagales pollen and IgE-sensitisation due to cross reactivity to soybean proteins</td><td></td></tr><tr><td>Prevalence (North and Middle Europe)</td><td>Low</td><td>High</td><td>?</td></tr><tr><td>Prevalence (Southern Europe)</td><td>Low</td><td>Low</td><td>Occasionally asthma outbreaks in the past</td></tr><tr><td>Affected (age) group</td><td>(1) Infants/children (2) Adults</td><td>Adults/adolescents/Children</td><td>Exposed workers and citizens in close vicinity</td></tr><tr><td>Soybean allergens involved</td><td>Gly m 5, Gly m 6, Gly m 8</td><td>(1) Gly m 4 (2) Gly m 3 (presumably)</td><td>Gly m 1, Gly m 2</td></tr><tr><td>Allergen abundance</td><td>Moderate to high content (i.e. seed storage proteins Gly m 5, Gly m 6 and Gly m 8) in soy beans and related products</td><td>(1) Low content of Gly m 4 in soy beans and soy protein (0.01–0.1%) and related, less processed soy products; (2) Gly m 3 content not known</td><td>Not known</td></tr><tr><td>Thermal stability</td><td>High</td><td>Low</td><td>Moderate</td></tr><tr><td>Digestive stability</td><td>High</td><td>Low</td><td>Moderate</td></tr><tr><td>Elicitors (products)</td><td>Many soy products (including highly processed or refined soy products)</td><td>Mildly processed soy products (i.e. soy drinks, soy protein powder)</td><td>Unprocessed soybeans (i.e. during unloading)</td></tr><tr><td>Symptoms</td><td>Quick onset (minutes to 2 h) of potentially severe systemic reactions with various symptoms of anaphylaxis: mucosal (i.e. oropharyngeal), cutaneous (urticaria, angioedema, eczema flaring), airway-related (upper and lower airways), gastrointestinal and/or cardiovascular symptoms</td><td>Quick onset (2–30 min) mostly mild mucosal symptoms and/or rare systemic symptoms of anaphylaxis</td><td>Airworthy symptoms (i.e. allergic rhinoconjunctivitis and asthma symptoms) within few hours of exposure</td></tr><tr><td>Additional clinical features</td><td>Atopic eczema (i.e. in infants with soy allergy), sometimes also (potentially severe) reactions after other legumes, (i.e. peanut, lupine, seeds or tree nuts)</td><td>Commonly additional (multiple) clinical cross reactivities to other Bev v 1-related plant foods, (i.e. apple, hazelnut, cherry, plum, peach, carrot, celery)</td><td></td></tr><tr><td>Medical diagnosis</td><td>Risk of systemic allergic reaction to stable soybean proteins (Gly m 5, Gly m 6, and Gly m 8)</td><td>Fagales pollen/Bet v 1-related food allergy to cross reactive soy allergen</td><td>Allergic asthma and rhinoconjunctivitis due to soy protein inhalation</td></tr><tr><td>Avoidance</td><td>Advising avoidance of allergenic soy products, in most cases soy sauce and miso can be consumed</td><td>Gly m 4 No ingestion of large amounts of mildly processed or unprocessed soy products</td><td>Occupational avoidance strategies in situations of large soy protein exposure (unloading of soy shipments)</td></tr><tr><td>Product declaration</td><td>Mandatory on each soy containing product (EU law)</td><td>(Voluntary) additional warning on hardly processed soy products particularly for birch pollen allergic individuals</td><td></td></tr><tr><td>Technical solution</td><td>No general technical solution available</td><td>Thermic or pressure processing of soy to reduce content in labile soy proteins</td><td>Dust extractor in occupational settings</td></tr></tbody></table>
<figure><img src="image_228.png" /><figcaption>FIGURE 114 Diagnostic work-up in soy-related allergic reactions (representing food allergy class II in left column and class I in right column)</figcaption></figure>

**IgE Testing:**

Allergen-specific IgE:

* Soy extract,

* Gly m 5, Gly m 6, and Gly m 8

* Gly m 4 and/or Bet v 1.

**Comments**

* Soy extract-specific IgE is related to oral food challenge outcomes, but 95% positive predictive value (PPV) has not been obtained.<sup>1216,1660</sup> This test potentially yielded false negative or low titers in the case of clinical pattern B.<sup>1221</sup>

* Gly m 5 and Gly m 6-specific IgE are associated with severe allergic reactions to soy.<sup>1219,1227</sup>

* Gly m 8-specific IgE is the best predictor of soy allergy diagnosis in children<sup>1229</sup> and adults.

* Gly m 4-specific IgE is a useful diagnostic marker in cases of clinical pattern B.<sup>1221</sup>

* Interpretation of SPT and IgE (sensitization tests) outcomes is also shown in Figure 114. The results were clinically relevant only in cases of symptoms corresponding to soy ingestion.

**Oral food Challenge tests**

In case of an improbable relationship between soy ingestion and allergic reactions:

Depending on the clinical pattern (A – C), a titrated oral food challenge with soy products was performed.

A. Offending or another appropriate soy protein-containing product (soy powder, tofu, soy drink).

B. Preferably mildly processed soy protein-containing product (soy milk) with soy allergens of low abundance (i.e., Gly m 4).

C. If needed, mucosal challenge with titrated soy extracts or offending (unprocessed) soy products.

## 6 – Clinical management of soy allergy

The advice tailored to specific clinical patterns is indicated below (Table 53):

A. Avoidance of soy-containing products depending on the symptom-eliciting-dose. In case of severe reactions after a small dose, avoidance of small amounts, regardless of the grade of soy processing. In case of a mild reaction after a large dose, less strict avoidance is needed. Fermented soy products such as soy sauce and miso are much less allergenic than tofu and soy milk. Advising complete avoidance of all soy products impairs the quality of life of patients with soybean allergy.

B. Avoidance of larger amounts of soy products, particularly those that are hardly or mildly processed (i.e., due to thermal processing, heating, such as soy drinks and powder).

C. Avoidance of soy-containing (hull) protein inhalation

**Pharmacotherapy for treatment of accidental allergic reactions**

The treatment tailored to specific clinical patterns is indicated below:

A. Due to the risk of severe reactions after unintentional ingestion of soy-containing products, self-administered emergency medication is required.

B. Emergency medication (not mandatory) C: Symptomatic treatment as required

**Allergen-specific immunotherapy**

At present, commercially-available products for allergen-specific immunotherapy of soybean protein allergies are not available.
<figure><img src="image_228.png" /><figcaption>**FIGURE 114** Diagnostic work-up in soy-related allergic reactions (representing food allergy class II in left column and class I in right column)</figcaption></figure>

**IgE Testing:**

Allergen-specific IgE:

* Soy extract,

* Gly m 5, Gly m 6, and Gly m 8

* Gly m 4 and/or Bet v 1.

**Comments**

* Soy extract-specific IgE is related to oral food challenge outcomes, but 95% positive predictive value (PPV) has not been obtained.<sup>1216,1660</sup> This test potentially yielded false negative or low titers in the case of clinical pattern B.<sup>1221</sup>

* Gly m 5 and Gly m 6-specific IgE are associated with severe allergic reactions to soy.<sup>1219,1227</sup>

* Gly m 8-specific IgE is the best predictor of soy allergy diagnosis in children<sup>1229</sup> and adults.

* Gly m 4-specific IgE is a useful diagnostic marker in cases of clinical pattern B.<sup>1221</sup>

* Interpretation of SPT and IgE (sensitization tests) outcomes is also shown in **Figure 114**. The results were clinically relevant only in cases of symptoms corresponding to soy ingestion.

**Oral food Challenge tests**

In case of an improbable relationship between soy ingestion and allergic reactions:

Depending on the clinical pattern (A – C), a titrated oral food challenge with soy products was performed.

A. Offending or another appropriate soy protein-containing product (soy powder, tofu, soy drink).

B. Preferably mildly processed soy protein-containing product (soy milk) with soy allergens of low abundance (i.e., Gly m 4).

C. If needed, mucosal challenge with titrated soy extracts or offending (unprocessed) soy products.

## 6 – Clinical management of soy allergy

The advice tailored to specific clinical patterns is indicated below (Table 53):

A. Avoidance of soy-containing products depending on the symptom-eliciting-dose. In case of severe reactions after a small dose, avoidance of small amounts, regardless of the grade of soy processing. In case of a mild reaction after a large dose, less strict avoidance is needed. Fermented soy products such as soy sauce and miso are much less allergenic than tofu and soy milk. Advising complete avoidance of all soy products impairs the quality of life of patients with soybean allergy.

B. Avoidance of larger amounts of soy products, particularly those that are hardly or mildly processed (i.e., due to thermal processing, heating, such as soy drinks and powder).

C. Avoidance of soy-containing (hull) protein inhalation

**Pharmacotherapy for treatment of accidental allergic reactions**

The treatment tailored to specific clinical patterns is indicated below:

A. Due to the risk of severe reactions after unintentional ingestion of soy-containing products, self-administered emergency medication is required.

B. Emergency medication (not mandatory) C: Symptomatic treatment as required

**Allergen-specific immunotherapy**

At present, commercially-available products for allergen-specific immunotherapy of soybean protein allergies are not available.
# 7 - Clinical cases

## Case 1 (clinical pattern<sup>1229</sup>):

**History:** A boy aged 2 years and 9 months started to develop atopic eczema around his mouth four months after birth. He initially received blood examination at the age of eight months and was already sensitized to egg white, wheat, and soybean (total IgE 250 IU/ml, egg white 21.4 kU/ml, wheat 3.19 kU/ml, and soybean 0.99 kU/ml). He was advised by the doctor to avoid food intake. He was then brought to the hospital at the age of 2 years and 5 months to receive oral food challenges.

**In-vitro testing:** His laboratory findings at the age of 2 years and 4 months (first visit) were as follows: total IgE, 5650 IU/ml; egg white, 70 kU/ml; wheat, 3 kU/ml; and soybean 17.1 kU/ml (Gly m 8: 37.6 kU/ml, Gly m 5: 4.9 kU/ml, Gly m 6: 1.1 kU/ml).

**Diagnosis:** He then underwent soy product (tofu) challenge at the age of 2 years and 9 months, and consequently developed skin rash, sneezing, and coughing after ingesting 9 g of tofu.

**Recommendations:** Avoidance of tofu and soymilk, but not soy sauce, miso, and natto, was advised.

**Prognosis:** He had naturally outgrown soybean allergy 1 year later with soybean IgE 1.90 kUA/l.

## Case 2 (clinical pattern A: Food-dependent exercise-induced anaphylaxis (FDEIA):

**History:** Girl (16 years old), atopic dermatitis. After 20 minutes of bike riding, anaphylactic reaction (abdominal pain, dyspnea, semi-consciousness, generalized flushing and swelling, low blood pressure), subsequent emergency treatment, and hospitalization for two days occurred. Two similar reactions occurred before the bike riding. No food allergies to soy, peanuts, or other food items are known to date.

**SPT:** Tofu, soy milk, boiled green soybean, soybean flour weakly positive (half histamine-equivalent), miso, soy sauce, and soybean fibers negative.

**In-vitro testing:** Total IgE 542 IU/ml, specific IgE to soybean 34 kUA/l, peanut 1.3 kU/l, wheat, Omega-5-Gliadin, various pollens including birch pollen, and Gly m 4 were negative. Microarrayed specific IgE: Gly m 5 (β-conglycinin), Gly m 6 (glycinin), and Gly m 3 were positive; CCD was negative.

**Oral challenge:** Thirty minutes of exercise after ingestion of 200 g of tofu caused the development of severe urticaria and facial swelling. No reactions occurred after boiling green soybeans or soy milk, with or without exercise.

**Diagnosis:** FDEIA of the soybean allergen Gly m 5.

**Recommendation:** Four hours after ingestion of soybean products (particularly tofu), no exercise.

## Case 3

**History:** Male (52 years old), since the age of 42, severe birch pollen-induced rhinoconjunctivitis occurred after ingestion of raw apples, hazelnuts, or strawberry oral itch. Adverse events would occur after subcutaneous immunotherapy (SCIT) with nonmodified birch pollen extract with severe systemic reactions. At the age of 52, after soy dessert, there would be increasing local itch (after 5 min: mouth, palate; after 15 min: eyes) and complete eyelid swelling within 20-30 min, thus requiring emergency treatment and hospitalization overnight. In 2012, after ingesting three fresh apple pieces, local itching (3 min: mouth, palate) and burning sensation of the throat occurred after 15 min. Almost complete eyelid swelling, itchy eyes, stuffy nose would also occur, and after 30 minutes, itchy hives would appear in the upper limbs, needing subsequent emergency treatment.

**In-vitro testing:** Total IgE was 37 kU/l, specific IgE to Gly m 4: 2.3 kUA/l. In 2012, the Total IgE was 48.5 kU/l, specific IgE to Bet v 1: 24 kUA/l (almost 50% of the total IgE specific for Bet v 1, indicating strong sensitization to Bet v 1 with cross-reactivity to structurally-related allergens).

**Diagnosis:** Angioedema after soy milk ingestion due to Gly m 4 (Bet v 1-cross reactive soy allergen)

**Recommendations:** Strict avoidance of mildly processed soy protein products and raw apples is recommended, and great precaution should be taken with large amounts of raw, Bet v 1-cross reactive pome and stone fruits, tree nuts, and legumes. Cooked plant products without dietary restriction (due to thermal instability of Bet v 1-related allergens)

# 7 - Research and future perspectives

Novel soy allergens other than those approved by the WHO/ IUIS have been reported (https://allergome.org). Although the clinical characteristics of these allergens have not been sufficiently examined, further research is expected to improve the accurate diagnosis and understanding of cross-reactivity. The improvement of diagnostic performance by specific IgE testing has been examined. A fusion protein of Gly m 8 and the extension region of the α' subunit of Gly m 5 could potentially diagnose soy allergy in the Japanese pediatric population.<sup>1234</sup> This technology may be useful for producing novel allergen components with improved diagnostic accuracy. Although allergen immunotherapy for peanuts can have therapeutic effects and improve quality of life, allergen immunotherapy for soy allergy (clinical pattern A) has not been sufficiently examined, thus requiring further research.
# 7 - Clinical cases

## Case 1 (clinical pattern<sup>1229</sup>):

**History:** A boy aged 2 years and 9 months started to develop atopic eczema around his mouth four months after birth. He initially received blood examination at the age of eight months and was already sensitized to egg white, wheat, and soybean (total IgE 250 IU/ml, egg white 21.4 kU/ml, wheat 3.19 kU/ml, and soybean 0.99 kU/ml). He was advised by the doctor to avoid food intake. He was then brought to the hospital at the age of 2 years and 5 months to receive oral food challenges.

**In-vitro testing:** His laboratory findings at the age of 2 years and 4 months (first visit) were as follows: total IgE, 5650 IU/ml; egg white, 70 kU/ml; wheat, 3 kU/ml; and soybean 17.1 kU/ml (Gly m 8: 37.6 kU/ml, Gly m 5: 4.9 kU/ml, Gly m 6: 1.1 kU/ml).

**Diagnosis:** He then underwent soy product (tofu) challenge at the age of 2 years and 9 months, and consequently developed skin rash, sneezing, and coughing after ingesting 9 g of tofu.

**Recommendations:** Avoidance of tofu and soymilk, but not soy sauce, miso, and natto, was advised.

**Prognosis:** He had naturally outgrown soybean allergy 1 year later with soybean IgE 1.90 kUA/l.

## Case 2 (clinical pattern A: Food-dependent exercise-induced anaphylaxis (FDEIA):

**History:** Girl (16 years old), atopic dermatitis. After 20 minutes of bike riding, anaphylactic reaction (abdominal pain, dyspnea, semi-consciousness, generalized flushing and swelling, low blood pressure), subsequent emergency treatment, and hospitalization for two days occurred. Two similar reactions occurred before the bike riding. No food allergies to soy, peanuts, or other food items are known to date.

**SPT:** Tofu, soy milk, boiled green soybean, soybean flour weakly positive (half histamine-equivalent), miso, soy sauce, and soybean fibers negative.

**In-vitro testing:** Total IgE 542 IU/ml, specific IgE to soybean 34 kUA/l, peanut 1.3 kU/l, wheat, Omega-5-Gliadin, various pollens including birch pollen, and Gly m 4 were negative. Microarrayed specific IgE: Gly m 5 (β-conglycinin), Gly m 6 (glycinin), and Gly m 3 were positive; CCD was negative.

**Oral challenge:** Thirty minutes of exercise after ingestion of 200 g of tofu caused the development of severe urticaria and facial swelling. No reactions occurred after boiling green soybeans or soy milk, with or without exercise.

**Diagnosis:** FDEIA of the soybean allergen Gly m 5.

**Recommendation:** Four hours after ingestion of soybean products (particularly tofu), no exercise.

## Case 3

**History:** Male (52 years old), since the age of 42, severe birch pollen-induced rhinoconjunctivitis occurred after ingestion of raw apples, hazelnuts, or strawberry oral itch. Adverse events would occur after subcutaneous immunotherapy (SCIT) with nonmodified birch pollen extract with severe systemic reactions. At the age of 52, after soy dessert, there would be increasing local itch (after 5 min: mouth, palate; after 15 min: eyes) and complete eyelid swelling within 20-30 min, thus requiring emergency treatment and hospitalization overnight. In 2012, after ingesting three fresh apple pieces, local itching (3 min: mouth, palate) and burning sensation of the throat occurred after 15 min. Almost complete eyelid swelling, itchy eyes, stuffy nose would also occur, and after 30 minutes, itchy hives would appear in the upper limbs, needing subsequent emergency treatment.

**In-vitro testing:** Total IgE was 37 kU/l, specific IgE to Gly m 4: 2.3 kUA/l. In 2012, the Total IgE was 48.5 kU/l, specific IgE to Bet v 1: 24 kUA/l (almost 50% of the total IgE specific for Bet v 1, indicating strong sensitization to Bet v 1 with cross-reactivity to structurally-related allergens).

**Diagnosis:** Angioedema after soy milk ingestion due to Gly m 4 (Bet v 1-cross reactive soy allergen)

**Recommendations:** Strict avoidance of mildly processed soy protein products and raw apples is recommended, and great precaution should be taken with large amounts of raw, Bet v 1-cross reactive pome and stone fruits, tree nuts, and legumes. Cooked plant products without dietary restriction (due to thermal instability of Bet v 1-related allergens)

# 7 - Research and future perspectives

Novel soy allergens other than those approved by the WHO/ IUIS have been reported (https://allergome.org). Although the clinical characteristics of these allergens have not been sufficiently examined, further research is expected to improve the accurate diagnosis and understanding of cross-reactivity. The improvement of diagnostic performance by specific IgE testing has been examined. A fusion protein of Gly m 8 and the extension region of the α' subunit of Gly m 5 could potentially diagnose soy allergy in the Japanese pediatric population.<sup>1234</sup> This technology may be useful for producing novel allergen components with improved diagnostic accuracy. Although allergen immunotherapy for peanuts can have therapeutic effects and improve quality of life, allergen immunotherapy for soy allergy (clinical pattern A) has not been sufficiently examined, thus requiring further research.
# B18 - Peanut allergy

Sakura Sato, Kirsten Beyer, Motohiro Ebisawa

## Highlights

* IgE to peanut components is a valuable tool for the clinician to diagnose and manage peanut allergy in children and adults. Tests for specific IgE to some peanut allergen components are commercially available, such as Ara h 1, 2, 3, 6, 8, and 9.

* Knowing which allergen the patient is sensitized to can help to predict the severity of allergic reaction and prognosis. Sensitization to storage proteins, which has high stability, (e.g., Ara h 2 and Ara h 6) is associated with severe allergic reaction, whereas labile proteins are less likely to cause severe reactions.

## 1 - The allergen sources

The peanut (Arachis hypogaea) belongs to the legume family (Leguminosae). Peanuts are most commonly grown in China, followed by India and the United States of America (USA). There are many different known cultivars. Peanuts are a common trigger of food-induced anaphylaxis. In some parts of the world, such as Europe or the USA, peanuts are primarily consumed in its roasted form. They might be eaten as whole peanuts, peanut butter, peanut flips, or as an ingredient in various products. Peanuts can be roasted in the shell and sold as such, or they can be shelled, blanched, oven-roasted either dry or in oil, and ground for the production of peanut butter or be sprayed on peanut flips. In other parts of the world, such as Asia and Africa, raw peanuts are used more commonly as a cooking ingredient.

Peanuts have a high protein content of 24-29% and contain various allergens. The processing of peanuts seems to be important regarding their allergenicity as roasting at high temperatures likely promotes the formation of compact globular protein aggregates that can increase the allergenicity of Ara h 1 and 2 as well as the oleosins, whereas cooking might reduce their allergenicity. In addition, peanut oil is commonly used, and its refined form can be safely consumed by most peanut-allergic individuals, whereas unrefined oil can contain amounts of allergens sufficient enough to trigger allergic reactions in some of the same individuals.

## 2 - Allergen families

A number of peanut allergens have been identified. Many of them have protective functions or are seed storage proteins. Peanut allergens belong to diverse protein families as prolamins, cuspins, profilin, Bet v 1-like pathogenesis-related (PR)-10 proteins, lipid transfer proteins (LTPs), defensins, and oleosins (Table 54). Recently, a protein that belongs to the cyclophilin family was identified.¹⁶⁶¹ Peanut proteins lead to IgE-mediated cross-reactions

among different members of the legume family as do other plant foods, such as tree nuts.

## 3 - Allergenic molecules

Seventeen peanut proteins most commonly involved in allergic reactions to peanut have been identified and officially accepted by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Subcommittee (Table 54, Figure 115). Ara h 1, Ara h 2, and Ara h 3 are considered peanut storage proteins and have high heat stability and digestive resistance. These allergens have been designated as major allergens, which were found to induce the greatest prevalence of IgE reactivity among allergic patients. Ara h 6 and Ara h 7 are also considered peanut storage proteins. Ara h 6 shares a part of IgE epitopes with Ara h 2 and is cross-reactive to Ara h 2.¹⁹¹ Ara h 5 is a minor allergen and is homologous with pollen profilins. Ara h 8, a PR-10 protein, has been shown to be a major allergen for patients with combined birch pollen and peanut allergies. Lipid transfer protein (LTP), a pan-allergen with a degree of cross-reactivity comparable to profilin, is present in peanuts as Ara h 9, Ara h 16, and Ara h 17. Ara h 10, Ara h 11, Ara h 14, and Ara h 15 belong to the peanut lipophilic allergen group, oleosin. Defensins are presented in the complex peanut lipophilic matrix as Ara h 12 and Ara h 13. Ara h 18 was recently identified and belongs to the cyclophilin family¹⁶⁶⁶.

## 4 - Sensitization to individual molecules and their clinical relevance

Sensitization rates are mainly based on the skin prick test (SPT) or specific IgE measurements with regard to whole peanut extracts. The sensitization rates vary widely depending on the age, comorbidities and other inhalant allergies of the tested population. Clinically not relevant sensitization seems to be especially high in patients with a coexisting pollen allergy, whereas clinically relevant sensitization is much higher in children with eczema. In an Australian study, it has been shown that infants with eczema are 8 times more likely to develop a peanut sensitization and 11 times more likely to have a peanut allergy than infants without eczema.¹⁶⁶² Screening a nonselected cohort of 13,100 German children of the general population aged 3-17 years demonstrated that almost 11% of the children were sensitized to peanuts¹⁶⁶³. The study of EuroPrevall on the prevalence of sensitizations to foods in adults revealed that peanut extract sensitization rates differed between 0.5-7.2% and that the region with the greatest prevalence of those with a peanut sensitization Madrid.¹¹⁴⁶ The prevalence of peanut sensitization predominantly results from a cross-reactivity to pollen and does not reflect the rate of peanut allergy. The majority of the peanut-allergic patients are sensitized to Ara h 2, whereas sensitization to Ara h 2 was lower in children of the general population.¹²³¹ Geographical differences were observed in sensitization rates to Ara h 8 and Ara h 9, which
# B18 - Peanut allergy

Sakura Sato, Kirsten Beyer, Motohiro Ebisawa

## Highlights

* IgE to peanut components is a valuable tool for the clinician to diagnose and manage peanut allergy in children and adults. Tests for specific IgE to some peanut allergen components are commercially available, such as Ara h 1, 2, 3, 6, 8, and 9.

* Knowing which allergen the patient is sensitized to can help to predict the severity of allergic reaction and prognosis. Sensitization to storage proteins, which has high stability, (e.g., Ara h 2 and Ara h 6) is associated with severe allergic reaction, whereas labile proteins are less likely to cause severe reactions.

## 1 - The allergen sources

The peanut (*Arachis hypogaea*) belongs to the legume family (Leguminosae). Peanuts are most commonly grown in China, followed by India and the United States of America (USA). There are many different known cultivars. Peanuts are a common trigger of food-induced anaphylaxis. In some parts of the world, such as Europe or the USA, peanuts are primarily consumed in its roasted form. They might be eaten as whole peanuts, peanut butter, peanut flips, or as an ingredient in various products. Peanuts can be roasted in the shell and sold as such, or they can be shelled, blanched, oven-roasted either dry or in oil, and ground for the production of peanut butter or be sprayed on peanut flips. In other parts of the world, such as Asia and Africa, raw peanuts are used more commonly as a cooking ingredient.

Peanuts have a high protein content of 24-29% and contain various allergens. The processing of peanuts seems to be important regarding their allergenicity as roasting at high temperatures likely promotes the formation of compact globular protein aggregates that can increase the allergenicity of Ara h 1 and 2 as well as the oleosins, whereas cooking might reduce their allergenicity. In addition, peanut oil is commonly used, and its refined form can be safely consumed by most peanut-allergic individuals, whereas unrefined oil can contain amounts of allergens sufficient enough to trigger allergic reactions in some of the same individuals.

## 2 - Allergen families

A number of peanut allergens have been identified. Many of them have protective functions or are seed storage proteins. Peanut allergens belong to diverse protein families as prolamins, cuspins, profilin, Bet v 1-like pathogenesis-related (PR)-10 proteins, lipid transfer proteins (LTPs), defensins, and oleosins (Table 54). Recently, a protein that belongs to the cyclophilin family was identified.¹⁶⁶¹ Peanut proteins lead to IgE-mediated cross-reactions

among different members of the legume family as do other plant foods, such as tree nuts.

## 3 - Allergenic molecules

Seventeen peanut proteins most commonly involved in allergic reactions to peanut have been identified and officially accepted by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Subcommittee (Table 54, Figure 115). Ara h 1, Ara h 2, and Ara h 3 are considered peanut storage proteins and have high heat stability and digestive resistance. These allergens have been designated as major allergens, which were found to induce the greatest prevalence of IgE reactivity among allergic patients. Ara h 6 and Ara h 7 are also considered peanut storage proteins. Ara h 6 shares a part of IgE epitopes with Ara h 2 and is cross-reactive to Ara h 2.¹⁹¹ Ara h 5 is a minor allergen and is homologous with pollen profilins. Ara h 8, a PR-10 protein, has been shown to be a major allergen for patients with combined birch pollen and peanut allergies. Lipid transfer protein (LTP), a pan-allergen with a degree of cross-reactivity comparable to profilin, is present in peanuts as Ara h 9, Ara h 16, and Ara h 17. Ara h 10, Ara h 11, Ara h 14, and Ara h 15 belong to the peanut lipophilic allergen group, oleosin. Defensins are presented in the complex peanut lipophilic matrix as Ara h 12 and Ara h 13. Ara h 18 was recently identified and belongs to the cyclophilin family¹⁶⁶⁶.

## 4 - Sensitization to individual molecules and their clinical relevance

Sensitization rates are mainly based on the skin prick test (SPT) or specific IgE measurements with regard to whole peanut extracts. The sensitization rates vary widely depending on the age, comorbidities and other inhalant allergies of the tested population. Clinically not relevant sensitization seems to be especially high in patients with a coexisting pollen allergy, whereas clinically relevant sensitization is much higher in children with eczema. In an Australian study, it has been shown that infants with eczema are 8 times more likely to develop a peanut sensitization and 11 times more likely to have a peanut allergy than infants without eczema.¹⁶⁶² Screening a nonselected cohort of 13,100 German children of the general population aged 3-17 years demonstrated that almost 11% of the children were sensitized to peanuts¹⁶⁶³. The study of EuroPrevall on the prevalence of sensitizations to foods in adults revealed that peanut extract sensitization rates differed between 0.5-7.2% and that the region with the greatest prevalence of those with a peanut sensitization Madrid.¹¹⁴⁶ The prevalence of peanut sensitization predominantly results from a cross-reactivity to pollen and does not reflect the rate of peanut allergy. The majority of the peanut-allergic patients are sensitized to Ara h 2, whereas sensitization to Ara h 2 was lower in children of the general population.¹²³¹ Geographical differences were observed in sensitization rates to Ara h 8 and Ara h 9, which