# Pollen-Food Allergy Syndrome: Allergens, Clinical Insights, Diagnostic and Therapeutic Challenges
## 3 PFAS Epidemiology  
While precise global prevalence rates for PFAS are difficult to determine due to geographical variability, it is estimated to affect 5-8% of the general population and up to 50-70% of individuals with pollen sensitization [33; 44; 45]. It is also challenging to determine specific prevalences of PFAS to different allergens due to the typically small size of studies, significant variability in methodology, and notable differences even among populations with similar allergen exposures, which can be influenced by genetic, dietary, and environmental factors [46]. PFAS is more frequently observed in regions where certain pollens, such as birch, ragweed, or grass pollens, are highly prevalent. The specific foods that trigger PFAS are closely tied to regional pollen sensorizations and local dietary habits, reflecting a dynamic interplay between environmental exposure and cultural food preferences. For example, birch pollen-related PFAS is more common in Northern and Central Europe [31, 47]. Birch pollen contains the major allergen Bet v 1, a PR-10 protein known for its strong cross-reactivity with homologous proteins in many plant-based foods, such as apples, pears, cherries, carrots, and celery [48]. This strong cross-reactivity explains why PFAS associated with birch pollen is one of the most frequently observed forms of the syndrome in these regions. In contrast, ragweed pollen-related PFAS is more dominant in North America, Central and Eastern Europe, and Japan [49]. Ragweed, particularly common ragweed (_Ambrosia artemisiiifolia_), produces large quantities of highly allergenic pollen, making it a significant contributor to allergic rhinitis and PFAS in these areas [6]. The allergens Amb a 8 (profilin) and Amb a 6 (LTP) cross-react with proteins in foods such as melons, bananas, and cucumbers, leading to the development of PFAS symptoms in sensitized individuals [42, 50]. The prevalence of ragweed-related PFAS in North America is partly due to the widespread distribution of ragweed and its ability to thrive in urban and suburban environments, further exacerbated by climate change and increased pollen production. In Central and Eastern Europe, ragweed has become an invasive species [51, 52], significantly increasing its impact on public health, including the prevalence of PFAS. Similarly, in Japan, ragweed-related cases are rising, likely due to environmental factors and increased awareness of cross-reactivity [53]. In Mediterranean countries, LTPs play a significant role in PFAS, with peaches (which contain the Pru p 3 LTP) being a major trigger, alongside other fruits like apricots, plums, and nectarines, which are staples of the local diet [54, 55]. Cultural factors also influence PFAS triggers. For example, soy and soy-based products, such as tofu and soy milk, are significant triggers in East Asian countries and Japan, where soy is a dietary staple [56]. The allergen Gly m 4, a PR-10 protein in soy, cross-reacts with birch and other pollens, making soy a frequent cause of PFAS in these regions. In Mexico, pineapples are a notable PFAS trigger, likely related to the local dietary prominence of this fruit and its cross-reactivity with pollens such as oak and ash [57]. These regional differences highlight how the type of pollen prevalent in a given area directly influences the pattern of PFAS, demonstrating the interplay between environmental exposure and dietary habits in shaping the epidemiology of the syndrome [49, 57]. Geographical differences are also influenced by cultural dietary habits, as the types of foods associated with PFAS vary depending on local cuisine and the availability of fresh produce [58, 59]. In regions where raw fruits and vegetables are frequently consumed, the risk of triggering PFAS symptoms may be higher. These findings underscore the importance of understanding local allergen profiles and dietary practices when diagnosing and managing PFAS in diverse populations.