Rice (Oryza sativa) allergy in rhinitis and asthma patients: a clinico-immunological study

Sensitization to foods varies in different countries reflecting a possible interaction of genetic factors, cultural and dietary habits. Rice is a major food consumed world wide and needs evaluation for IgE mediated reactions. The present study was carried out to identify rice allergy in patients of rhinitis and asthma and identify the allergenic proteins in raw and cooked rice. Of 1200 patients screened using standard questionnaire, 165 presented with history of rice allergy. Of these, 20 (12.1%) patients demonstrated marked positive skin prick test (SPT) and 13 showed significantly raised specific IgE to rice compared to normal controls. Double blind placebo controlled food challenge (DBPCFC) confirmed rice allergy in 6/10 patients. Immunoblot with hypersensitive individual patients' sera showed 14-16, 33, 56 and 60 kDa proteins as major IgE-binding components in rice. Boiled rice retained four IgE reactive proteins of 16, 23, 33 and 53 kDa. In summary, IgE-mediated rice allergy affects 0.8% [(0.42-1.58) at 95% CI] of asthma and rhinitis cases. The subjects with severe SPT reactions (4 mm or above) and specific IgE, 6.9 ng/ml to rice demonstrated positive blinded food challenge with clinical symptoms.