Sensitization to lupine flour: is it clinically relevant?

Background Lupinus angustifolius (blue lupine) is used for human and animal consumption. Currently, the lupine content in bread varies from 0% to 10% and from 0.5% to 3% in pastry. Although lupine flour is present in many products, anaphylaxis on lupine flour is rarely seen. Objective The aim of our study was to determine the clinical relevance of sensitization to lupine flour. Methods From October 2004 until October 2005, we performed skin prick tests (SPT) with lupine flour, peanut and soy extracts in consecutive patients attending our allergy clinic with a suspected food allergy. In patients sensitized to lupine flour, double-blind placebo-controlled food challenges (DBPCFC) were performed and specific IgE was measured. Results We tested 372 patients. SPTs with peanut, soy and lupine flour were positive in 135, 58 and 22 patients, respectively. Nine patients with sensitization to lupine flour underwent DBPCFC, which was negative in eight cases. In contrast, one patient experienced significant symptoms. Four of these nine patients suspected lupine by history. Two other patients with a positive history to lupine declined from challenges. In these patients, a 3-day dietary record showed that they could consume lupine without symptoms. Specific IgE in the serum was positive for L. angustifolius, peanut and soy in all nine patients. Conclusion These results demonstrate that clinical lupine allergy is very uncommon, even in the presence of sensitization to lupine flour. The estimated prevalence of lupine allergy, among patients with a suspected food allergy, referred to a tertiary allergy centre in the Netherlands is 0.27-0.81%. In most, although not all cases, sensitization is not clinically relevant and is most likely caused by cross-sensitization to peanut. In selected cases, eliciting doses are low, making significant reactions possible.