Contact urticaria from rice

A 30-year-old man with atopic dermatitis had had erythema and itching of th e hands after washing rice in water, though he had always eaten cooked rice without problems. Handling test with water used to wash regular rice was p erformed on abraded hands, and produced urticarial erythema after several m inutes. Applications of water used to wash allergen-reduced rice were negat ive for urticarial reaction. Prick test with water used to wash regular ric e was +++. However prick test reaction with water used to wash allergen-red uced rice was +. Histamine-release test of regular rice-washing water was g rade 3 and that of allergen-reduced rice grade 1. In immunoblotting analysi s with regular rice washing water, there were no bands with this patient. T hese results suggest that the allergen responsible for contact urticaria in this patient might be water-soluble, heat-unstable, and not contained in a llergen-reduced rice.