Cross-allergenicity of peanut and lupine:: The risk of lupine allergy in patients allergic to peanuts

Background: Peanut allergy is common, but cross-allergy between legumes is rare, Proteins from Lupinus albus are increasingly eaten in the form of seeds or additives to wheat flour, The risk of cross-allergenicity is still insufficiently known, Objective: We sought to study the risk of cross-allergy to lupine in patients allergic to peanut and to study lupine allergenicity, Methods: Twenty-four patients allergic to peanuts were studied by means of skin prick tests with native lupine flour from Lupinus albus. Double-blind oral challenge tests were performed with lupine flour and peanut in 8 of these patients. Specific IgEs were assayed for peanut, lupine flour, and pollen in 6 sera. RAST inhibition tests for lupine pollen by peanut were performed on 4 of these sera. Peanut and lupine flour immunoblots were carried out for 6 sera, and crossed immunoblot inhibitions for peanut by lupine flour and lupine flour by peanut were carried out for 2 sera. Results: The skin prick test responses with lupine flour were positive in 11 (44%) subjects. The challenge test responses mere positive in 7 of 8 subjects at the same doses as with peanut. The major lupine flour allergen (molecular mass, 43 kd) is present in peanuts. The RAST inhibition and immunoblot tests indicated cross-reactivity of peanut with the lupine flour and pollen. Conclusions: The risk of crossed peanut-lupine allergy is high, contrary to the risk with other legumes. The inclusion of 10% lupine flour in wheat flour without mandatory labeling makes lupine a hidden allergen, presenting a major risk of cross-reaction in subjects already allergic to peanut products, A high sensitizing potential can also be postulated for this legume.