Cross-reactivity of IgE antibodies with allergens in birch pollen, fruits and vegetables.

Allergens extracted from apple, carrot, celery tuber and orange were coupled to radioallergosorbent test (RAST) discs. These and commercial birch, mugwort and timothy pollen discs were used to study sera from 90 patients for the presence of IgE antibodies which react with the allergens in question. Individual sera frequently gave positive results with several discs - in particular with birch pollen, apple, carrot and celery tuber discs. If IgE antibodies to birch pollen or apple allergens were detected, there was a 90% chance of antibodies being found also to the second one of these two source materials. Skin tests and patient histories indicated similar clustering of allergies. RAST inhibition experiments showed that the clustering phenomenon was due to cross-reactivity. All immunological determinants in fruits and vegetables appeared to be present also in birch pollen, but all birch pollen determinants were not present in fruits and vegetables. 45 children with atopic dermatitis were studied to establish whether a positive orange RAST would correlate with a history of atopic dermatitis aggravated by orange. The results were negative.