# Pollen Food Allergy Syndrome in Southern European Adults: Patterns and Insights
## 3 Results
### Epidemiology of PFAS/OAS  
There is a wide variety of PFAS prevalence in different geographical regions. Rates between 4.7% and more than 20% have been reported in children, and 13% to 53.8% in adults [20]. Studies aiming to determine the prevalence of PFAS often begin with populations that include individuals with allergic rhinitis, and sensitivities to aeroallergens associated with PFAS. This selection bias may lead to artificially elevated prevalence rates. Additionally, epidemiological studies face limitations such as varying definitions of PFAS and OAS, the underreporting of symptoms that do not significantly affect the daily quality of life, and underdiagnosis in individuals often labeled as 'picky eaters'.  
In Asia, South Korea is the country with apparently the highest prevalence of PFAS (42.7%) [21], followed by Japan (34.6%) [22]. However, differences in study methodologies, including the use of the ImmunoCAP ISAC (ImmunoSlid-phase Allergy Chip, Thermo Fisher Scientific, Uppsala, Sweden) in the Japanese study and skin prick tests/specific IgE in the South Korean study, may contribute to these variations rather than reflecting true regional differences. In a study performed in Armenia, its prevalence in young adults was 13% [23]. PFAS appears to be less widespread in the USA; a previous study, conducted using a mailed questionnaire, reported median estimates of the prevalence of OAS among the patients with pollen allergy were 5% among children and 8% in adults [24]. In Australia, the outcomes of a study performed in children and adolescents showed that the prevalence of OAS was 14.7%, while that of PFAS was 4.9% [25].  
In Europe, particularly in central and northern areas, sensitization to the Bet v 1 allergen contained in Birch pollen is the main cause of seasonal allergic rhinitis, as well as of PFAS, elicited by the ingestion of plant foods containing Bet v 1-homologous PR-10 proteins, such as Mal d1 in apple and Cor a1 in hazelnut [20; 26]. In Europe, PFAS also occurs in allergic rhinitis patients who have been sensitized to panallergens present in the pollen of Grass or Ragweed. The rise in temperatures due to the climate change is leading to a lengthening of the pollen season, increasing the prevalence of allergic rhinitis and therefore growing the prevalence of PFAS [16].  
There is a higher incidence of PFAS in countries of Northern Europe, compared to the southern ones. The influence of Birch and Ragweed on the prevalence of PFAS in Europe is evident, with reports indicating a prevalence of 40-50% among patients with pollen allergies [4; 27]. In contrast, the prevalence is approximately 20% in the Mediterranean region, which is free of this pollen [28]. In pediatric studies performed in Sweden and the United Kingdom, the prevalence of PFAS was estimated to be 25% and 48%, respectively [29; 30]. As far as the pediatric population in the Mediterranean area of South Europe is regarded, the prevalence of PFAS is estimated as follows: 35.9% in an Italian population, while another one estimated it in 27% of the ones with seasonal allergic rhinitis [10; 31], 29.7% in Croatia [32], 16% in French children with asthma [33], and 3.3% in Turkish children with respiratory allergies [34].