Over the last three decades several authors have described the existence of an association between sensitivity to different pollens and sensitivity to diverse edible vegetables. Most patients with birch pollen allergy report oral allergy symptoms after eating fresh apples and other vegetable foods. Major birch pollen and apple allergens, Bet v 1 and Mal d 1, and other antigens are highly homologous; as a consequence, pollen-specific immunotherapy (SIT) might be expected to improve apple hypersensitivity. A prospective study was carried out in 27 birch pollen-sensitive patients with apple-induced OAS (oral allergy syndrome) who received injection immunotherapy for 24, or 36 months. Eight patients not submitted to SIT and followed up for 24-36 months were used as a control. Sixteen patients (59%) reported a significant reduction (37%) or a total disappearance (22%) of OAS symptoms after SIT.
Conclusion: SIT with birch pollen extracts effectively reduces clinical apple sensitivity in some cases; these effects are not paralleled by a similar reduction of specific IgE and skin reactivity.