IgE-mediated sensitization to galactose-alpha-1,3-galactose (α-gal) in urticaria and anaphylaxis in Spain: geographical variations and risk factors.

BACKGROUND The aims of this study were to investigate the prevalence of sIgE to galactose-alpha-1,3-galactose (α-gal) in individuals with acute urticaria or anaphylaxis from different geographical areas of Spain and to evaluate the relevance of demographics and lifestyle as risk factors for this immune response. METHODS Participants were recruited from allergy departments at 14 Spanish hospitals. Patients aged 18 years or older presenting with urticaria or anaphylaxis were enrolled into one of two arms: cases and controls. An interviewer-administered questionnaire collecting demographic data, lifestyle habits, and the presence of cofactors was obtained from each participant. sIgE to α-gal and total IgE were determined using ImmunoCAP®. sIgE levels ≥0.35 kU/l were considered a positive result. RESULTS The study population comprised 160 cases and 126 controls. The median age was 44 years. The overall prevalence of a positive result of sIgE to α-gal was 15.7%; this was higher in cases (26.3%) than in controls (2.4%). The sIgE anti α-gal positivity rate ranged from 37.68% (rural) to 15.38% (semi-urban) and 7.85% (urban). The rates of positivity were 46.32%, (Northern), 0.72% (Center), and 0% (Mediterranean). A positive result of sIgE to α-gal associated with history of tick bites, participation in outdoor activities, pet ownership, and ingestion of mammalian meats or innards before the onset of symptoms. Only alcohol consumption could be implicated as a cofactor. CONCLUSIONS Sensitization to α-gal in patients with urticaria or anaphylaxis differs considerably between the three geographical areas studied and is related to tick bites.