Cross-reactivity from poppy seed to buckwheat in a food allergic patient with poppy seed anaphylaxis

Abstract

Rationale The opium poppy, Papaver somniferum L., is the source of both poppy seeds and opium. The commercially available seeds are widely used as ingredients for various kinds of food. IgE-mediated sensitization to poppy seeds is rare but if present, clinical symptoms are usually severe. Cross-reactivity between poppy seeds and other food allergens have been described with sesame, hazelnut, rye grain and kiwi fruit. We report a novel cross-reactivity with buckwheat in a 17-year-old female with poppy seed anaphylaxis. Methods Skin prick test, CAP-FEIA, CAP-inhibition tests, immunoblotting, immunoblot-inhibition and open oral food challenge tests were performed. Results Prick tests with native poppy seeds were strongly positive. Total serum IgE was raised to 646 kU/l, and allergen specific IgE against poppy seed (287 kU/l), hazelnut, sesame, buckwheat, brasil nut, pistachio, cashew nut and almond was detected by CAP-FEIA. CAP inhibition tests demonstrated a cross-reactivity from poppy seed to buckwheat but not to natural rubber latex. Immunoblotting of poppy seed extracts with our patients serum revealed 4 distinct allergen bands, which were inhibited after preincubation with buckwheat extract. The immunoblot for opium latex or raw opium was negative. Oral food challenge with up to 10 g of unground poppy seeds were negative, whereas 1 g of ground poppy seeds led to urticaria, heat sensation, pruritus, conjunctivitis and dyspnoe followed by a threefold raise of mast cell tryptase in serum (5.4 to 17.6 μg/l) within 3 hours. Conclusions Buckwheat must be considered as a novel cross-reactive allergen in at least some poppy seed allergic patients.