Effect of tree pollen specific, subcutaneous immunotherapy on the oral allergy syndrome to apple and hazelnut

Background: The efficacy of specific immunotherapy (SIT) in pollen allergy is well established. However, its effect on pollen associated food allergy particularly the oral allergy syndrome (OAS) is not definitely ascertained. Objective: The purpose of this controlled prospective study was to investigate whether SIT with tree pollen, mainly birch, has an effect on OAS induced by apple or hazelnut in birch pollen-allergic individuals. Methods: Twenty-seven birch pollen-allergic subjects with OAS induced by apple or hazelnut underwent open oral provocation tests (OPT) with increasing doses (1 to 128 g) of fresh apple or ground hazelnut 1 year apart. Fifteen of 27 subjects were treated with SIT and 12 were not. Skin-prick test with birch pollen, apple and hazelnut, and specific serum IgE, IgG and IgG4 to rBet v 1, apple and hazelnut were determined. Results: Thirteen of 15 (87%) SIT-treated subjects could eat significantly (P < 0.001) more of apple or hazelnut without any symptoms/signs. The average tolerated quantity increased from 12.6 to 32.6 g apple after 1 year in this group. In contrast, only one of 12 (8%) individuals without SIT was able to consume a higher amount without symptoms. On evaluating laboratory parameters, only IgG4 antibodies to rBet v 1 were found to be significantly (P < 0.01) increased in the SIT-treated group after 1 year. Conclusions: The study shows that SIT with extracts containing birch pollen has a positive impact on OAS to apple or hazelnut in birch pollen-allergic individuals. In spite of this outcome, the amount of apple/hazelnut tolerated is still small. Thus, the effect of SIT on the patients' management of OAS remains limited.