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Background: Cholinergic urticaria (CholU) is a common type of chronic inducible urticaria, characterized by small itchy wheals that appear upon physical exercise or passive warming. Malassezia globosa, a skin resident fungus, has been identified as an antigen that induces mast cell/basophil degranulation and wheal formation through specific IgE, in Japanese patients with atopic dermatitis and CholU. In this study we aimed in assessing the rate of IgE sensitizations against skin resident fungi in European CholU patients. Methods: We assessed serum IgE levels to Malassezia furfur, Candida albicans and Trichophyton mentagrophytes using routine lab testing and Malassezia globosa using a newly established ELISA. We correlated the results to wheal formation and other clinical features. Results: Four patients (of 30 tested) had elevated levels of IgE against Malassezia furfur and Candida albicans and two had elevated levels of IgE against Trichophyton mentagrophytes. Four sera (of 25 tested) had elevated levels of IgE to the Malassezia globosa antigen supMGL_1304. Sensitization to one skin fungus was highly correlated with sensitization to the other tested fungi. We saw highly significant correlations of sensitization to supMGL_1304 with wheal size in the autologous sweat skin test (r s = 0.7, P = 0.002, n = 19), the Erlangen atopy score (r s = 0.5, P = 0.03, n = 19), total IgE serum levels (r s = 0.5, P = 0.04, n = 19) and a positive screen for IgE against common airborne/inhalant allergens s (sx1; r s = 0.54, P = 0.02, n = 19). Conclusions: Sensitization to skin resident fungi including Malassezia globosa is uncommon in European CholU patients, but is associated with atopy and pronounced wheal formation upon dermal contact with their own sweat.

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