Profiles of birch sensitization (Bet v 1, Bet v 2, and Bet v 4) and oral allergy syndrome across Italy

Background: Birch allergy (BA) is a common pollinosis caused by the allergens Bet v 1, Bet v 2, and Bet v 4. Oral allergy syndrome (OAS) is frequently associated with BA. A gradient of sensitization to birch allergen across Europe has been reported. Therefore, this study aimed to investigate the birch sensitization profile, including OAS, across Italy. Methods: We performed a retrospective study of 854 patients (391 males, mean age 35.9 years, range 18-93 years): 196 patients were recruited in Genoa, 188 in northern Italy, 359 in central Italy, and 111 in southern Italy. Serum IgE to Bet v 1, Bet v 2, and Bet v 4 was assessed, and OAS was analyzed. Results: With respect to the geographical path Genoa-North-Center-South, the frequency of sensitization to Bet v 1 decreased significantly (P<.0001) from Genoa (95.41%) to southern Italy (58.56%). The frequency of sensitization to Bet v 2 increased significantly (P<.0001) from Genoa (6.12%) to southern Italy (52.25%). The frequency of Bet v 4 also increased significantly (P=.0002) from Genoa (6.12%) to southern Italy (14.41%). The distribution of patients with OAS differed significantly across the areas (P<.0001), the most marked difference ranging between 33.5% in Genoa and 76.9% in northern Italy. The frequency of birch allergens correlated with OAS in central Italy only. Conclusions: The present study demonstrated a significant difference between sensitization to birch and its clinical expression across Italy.