Frequent occurrence of IgE to seeds of rape, oilseed rape, mustard and soy in children suspected for food allergies

We have noted strongly positive skin prick test (SPT) reactions to seeds of Brassicaceae family foods, i.e., rape, oilseed rape and mustard in infants and children suspected for food allergies. Sensitization pathways are not known and some the youngest infants had been exclusively on breast-feeding. Extracts were prepared from seeds and used as solid-phase antigens in IgE ELISA and immunoblotting. Sera from 61 children (aged 3 months to 14 years), all with positive SPT to 1-4 of the foodstuffs, were analyzed. In ELISA 64% of the children showed clear IgE binding to rape, 61% to oilseed rape, 69% to mustard, and 38% to soy. Parallel IgE binding to rape, oilseed rape and mustard was common and correlated to the intensity of SPT reactions and serum IgE levels. In IgE immunoblotting major reactivity was to a 9-11 kDa protein which was partially purified by reversed-phase-HPLC and shown to bind IgE from the patient sera in ELISA. Children reacting to seeds of rape, oilseed rape and mustard in SPT show also frequently IgE antibodies in ELISA. Major IgE binding allergen seems to be a 9-11 kDa protein, but the route of sensitization and its clinical importance remain to be elucidated.