Anaphylactic reaction to lupine flour

Summary Roasted lupine seeds have been used as snack food in Mediterranean countries for years. Since the 1990s, lupine flour has been used as a substitute for or additive to other flours in countries of the European Union; usually the amount is so low that no declaration is required. Since 1994, a number of cases of immediate‐type allergy to lupine flour‐containing products have been published. A 52‐year‐old woman developed facial and mucosal edema, followed by dizziness and shortness of breath a few minutes after ingestion of a nut croissant con‐taining lupine flour; she required emergency care. Allergy diagnostic tests revealed a total IgE of 116 kU/l, a highly elevated concentration of IgE specific for lupine seed (42.9 kU/l) and birch pollen IgE of 2.57 kU/l. Skin prick test with native lupine flour was strongly positive. Allergy against lupine seeds may develop de novo or via cross‐reactivity to legumes, particularly peanuts, the latter being detectable in up to 88% of cases, founded on a strong sequence similarity between lupine and peanut allergens. In our patient, no cross‐reactivity could be detected via immunoblotting, indicating a rare monovalent sensitization to lupine flour. Treatment consists of avoidance of lupine flour‐containing products. Patients with proven peanut allergy should also avoid lupine flour because of the major risk of cross‐reaction.