Crossed line immunoelectrophoresis (CLIE) was used to show that a minor allergen present in birch pollen and another present in timothy pollen shared common epitopes with antigens in apple, carrot and celery tuber. Major pollen allergens were not involved. Structural similarities were also noticed in some mugwort pollen antigens and antigens in apple, carrot and celery, but none of these mugwort antigens acted as an allergen. In crossed immunoelectrophoresis (CIE) of samples of apple, carrot or celery extracts towards antibodies against birch pollen, grass pollen or mugwort pollen, four to 14 distinct precipitates were observed and shown to be specific. In crossed radioimmunoelectrophoresis (CRIE) none of the precipitates could be shown to act as an allergen. Using allergen detection on nitrocellulose paper, the apple, carrot and celery extracts were shown to possess IgE-binding capacity.