C A S E R E P O R T S EUR ANN ALLERGY CLIN IMMUNOL VOL 49, N 3, 143-144, 2017 KEY WORDS food allergy; IgE; omalizumab; oral allergy syndrome; treatment Corresponding author Riccardo Asero Ambulatorio di Allergologia, Clinica San Carlo Via Ospedale 21 20037 Paderno Dugnano (MI), Italy E-mail: r.asero@libero.it Summary The first case of disappearance of apple-induced oral allergy syndrome in a birch pollen-al- lergic patient following omalizumab treatment is reported. This observation in a case of type 2 food allergy suggests that omalizumab is potentially an effective preventive treatment for patients with severe, type 1 food allergies. Ambulatorio di Allergologia, Clinica San Carlo, Paderno Dugnano, Italy Disappearance of severe oral allergy syndrome following omalizumab treatment R. ASERO Introduction It has long been known that birch pollen-allergic patients fre- quently develop oral itching with angioedema of the lips fol- lowing the ingestion of fresh foods and vegetables, due to the presence of allergen proteins homologous to the major birch pollen allergen, Bet v 1. This phenomenon is known as oral allergy syndrome (OAS). Although in most cases limited to the oral cavity, reactions may be sometimes severe enough to involve the pharynx and to prevent patients to eat a large spec- trum of fresh and raw fruits and vegetables, with a significant reduction of their quality of life. The apple is the fruit most frequently involved in such food allergies, due to the very high homology of its PR-10 allergen, Mal d 1, with Bet v 1 (1-4). Previous studies showed that allergen immunotherapy with birch pollen extracts may reduce or abolish secondary apple allergy (revised in [5]). Omalizumab, a humanized anti-IgE monoclonal antibody in- dicated for a long time in severe cases of allergic asthma, has been recently introduced also as a treatment for patients with refractory chronic urticaria. Omalizumab binds the Fc3 sub- unit of free IgE molecules and it is generally accepted that the reduced binding of free specific IgE to the high affinity IgE re- ceptor (FceRI) eventually leads to a reduced density of specific IgE on the surface of mastcells and basophils, and to the down- regulation of the receptor itself. In food allergy, omalizumab has been experimentally tried in cases of severe allergies both as a monotherapy (mainly in adults) (6-8) and as an add-on treat- ment to oral immunotherapy (OIT; virtually only in children) (9-12). In most cases, the drug was able to increase significantly the threshold dose of offending foods required to induce adverse reactions. No data about the effect of omalizumab in type 2 food allergies are available to date.