Lupin allergy and lupin sensitization among patients with suspected food allergy.

BACKGROUND Lupin, a legume with good nutritional value, is used in food production today, most often in bakery products. Lupin sensitization is often seen among patients with reactions to legumes, but the number of reports describing lupin anaphylaxis is also increasing. OBJECTIVE To investigate the occurrence of lupin sensitization, cross-reactivity, and lupin allergy among patients with suspected food allergy in Finland, where lupin is a labeled ingredient in few products. METHODS The occurrence of positive skin prick test (SPT) reactions to lupin seed flour was studied among 1522 patients with suspected food allergy from November 1, 2005, through December 31, 2007. Clinical histories and diagnostic SPT results were analyzed among patients with positive SPT results to lupin. For 1 patient, ImmunoSpot and lupin radioallergosorbent test inhibition methods were used. RESULTS Lupin sensitization was shown in 25 of 1522 patients (1.6%), and probable lupin allergy was diagnosed in 7 of 25 patients, in whom the clinical symptoms varied from anaphylaxis and respiratory symptoms to contact urticaria and itchy mouth. Cross-reactions or concurrent reactions to other legumes were seen in 18 of 25 patients. CONCLUSIONS Clinically relevant lupin allergy often occurs in patients without atopic background or other food allergies, although lupin sensitization most commonly seems to represent cross-reactivity to other legumes. The occurrence of lupin allergy in a country where lupin has not been traditionally used is surprisingly common, suggesting that short-term use of modest amounts of lupin can cause serious allergic reactions.