D1.91 - Characterization of Bet v1 Sensitized Patients in Madrid: A Real Life Study

Bet v1 is a major allergenic protein belonging to the PR-10 family, classically associated with birch pollen allergy. It is typically linked to respiratory symptoms and pollen-food allergy syndrome (PFAS). In Mediterranean areas such as Madrid, where birch trees are rare, Bet v1 sensitization is sometimes found among allergic patients. The aim of this study was to better understand the clinical significance of Bet v1 in a birch-free environment.

217 cases with positive specific IgE to Bet v1 confirmed by ImmunoCAP® testing were evaluated in a tertiary allergy center in Madrid between January 2020 and June 2024. Their clinical records were analyzed for demographic data, allergic symptoms and sensitization profiles. Co-sensitization to other plant-derived allergens including profilins, lipid transfer proteins (LTPs) and seed storage proteins were also evaluated.

The mean age of the patient cohort was 30.27 years. Most were Spanish-born (58%), though nearly one-third had origins outside Spain including North, Central and South America, Europe and Asia.

94.9% of the patients were diagnosed with allergic rhinitis and 51.1% with asthma. 23.5% of the patients were co-sensitized to profilins, 17.9% to LTPs, and 10.6% to storage proteins. Nearly all patients (95.3%) were co-sensitized to other pollens, being the most frequent grass and cypress pollen.

Food allergy affected 57.5% of the patients. The foods most commonly associated with allergic reactions were hazelnut (38.71%), peach (33.6%), apple (16.1%), and cherry (9.7%). Regarding tree nuts, walnut was the second most frequently reported trigger after hazelnut.

71 systemic reactions were documented in 46 patients and attributed to plant-based foods. Among these, 17 systemic reactions occurred in patients who were sensitized only to heat-labile proteins like Bet v 1 and/or profilin. 

Bet v1 sensitization might be found among allergic individuals in Madrid, despite the lack of birch pollen in the environment. This sensitization may be driven by cross-reactive allergens from local Fagales species such as Quercus, and this pattern may be shaped by environmental exposure, dietary habits, and individual immunological responses. Although PR-10 proteins are usually considered heat-labile and associated with milder symptoms, cases in this cohort show that severe reactions can still occur. These findings underscore the importance of considering regional and environmental factors when evaluating allergic disease.