Preheated autologous serum skin test in localized heat urticaria

Localized heat urticaria (LHU) is a rare type of physical urticaria, characterized by itching and erythema and well‐demarcated weals, appearing within minutes at heat‐exposed body sites. Its pathogenesis has not yet been clarified. We report the case of a 46‐year‐old woman with a generalized form of LHU, which was induced by exposure to warm baths, and consumption of warm food and drinks. Weal reaction was obtained 10 min after application of a metal cylinder heated to 43 °C. Interestingly, only serum previously heated to 56 °C and injected intradermally for autologous serum skin test induced a weal and flare reaction, whereas serum preheated to 45 °C did not induce any reaction. Our patient did not respond to high‐dose antihistamines, and refused a heat desensitization programme. Treatment with colchicine 1 mg/day or ciclosporin A 3.5 mg/kg/day for 1 month yielded no improvement. Mild improvement was obtained with intramuscular injection of triamcinolone acetonide 40 mg every 2 weeks for 2 months.