Seasonal variation in food allergy to apple

The aim of the study was to investigate the possibility of a seasonal varia tion in reactivity to apples in 27 birch pollen allergic patients. Before a nd during the birch pollen season 1998, the patients: were subjected to dou ble-blind, placebo-controlled food challenges (DBPCFCs) with grated fresh G olden Delicious apple followed by an open food challenge with whole fresh a pple. The clinical reactions elicited during the challenges were evaluated both by the patients and the investigators. Moreover, the skin reactivity a nd the in vitro reactivity to apple were evaluated by skin prick test (SPT) , leukocyte histamine release (HR), measurement of specific IgE, and immuno blotting experiments. The sensitivity of the DBPCFC, when compared with the result of the open challenge, was 0.74 (14/19) before the season and 0.80 (16/20) during the season. None of the patients reacted to the blinded chal lenge without a subsequent reaction to the open challenge. One placebo reac tion was registered both before and in season, but not in the same patient. The patient scores of the first positive challenges, and the maximal score s of each combined blinded and open challenge session, were significantly i ncreased during the pollen season (P < 0.05). The scores of the open challe nge were significantly higher than the scores of the DBPCFC both before the season and during the in-season challenges (P < 0.05). Specific IgE agains t Golden Delicious increased during season (P < 0.05), while neither SPT, H R, nor immunoblotting experiments could confirm an increase in reactivity. In conclusion, the results of the oral challenge tests indicated an increas e in clinical reactivity to apples during the birch pollen season in birch pollen allergic individuals. (C) 2001 Elsevier Science B.V. All rights rese rved.