Food contact hypersensitivity syndrome: the mucosal contact urticaria paradigm

Summary Oral allergy syndrome (OAS) or pollen–fruit allergy syndrome represents a mucosal allergic contact urticaria in people sensitized to common pollens, due to IgE cross‐reactivity between homologous pollen allergens and various plant foods. It is the most prevalent food allergy, affecting millions of people with respiratory allergies. Usually, symptoms are mild, self‐limiting and localized to the oropharyngeal mucosa, although they may sometimes become generalized and life‐threatening. Although patients usually recognize the offending foods, diagnosis may sometimes be complicated. Several clinical syndromes and association between pollens and plant‐derived foods have been described. Crossreactivity on the basis of stringent immunological and allergological criteria can also occur in people without pollen sensitization or concomitant respiratory allergies, as in latex–fruit syndrome. The term ‘food contact hypersensitivity syndrome’ (FCHS) is proposed in this paper for the first time, to include all mucosal hypersensitivity reactions presenting with contact to food (both immunological and nonimmunological), whether due to crossreactivity with homologous plant‐derived allergens or not. At this time, prophylaxis and treatment can only be attained by avoidance, even when symptoms are mild, with consequent impairment in quality of life. A better understanding of the pathophysiological mechanisms of FCHS and food allergy in general is essential for deeper insights and future emergence of effective therapies.