Cold urticaria patients exhibit normal skin levels of functional mast cells and histamine after tolerance induction.

Cold urticaria is a skin condition characterized by rapid appearance of itchy wheals and occasionally angioedema in response to cold stimulation. Antihistamines do not sufficiently protect all patients from symptoms, even when used in higher than standard doses. In these patients, desensitization to cold can be beneficial. The aim was to investigate whether desensitization can lower temperature thresholds and reduce release of histamine in the skin. Cold urticaria patients were subjected to desensitization and assessed for skin responses to cold stimulation and codeine before and after. Histamine levels mediated by cold and codeine were determined by cutaneous microdialysis before and after desensitization in patients and healthy controls. Desensitization to cold resulted in protection from cold-induced symptoms and lower temperature thresholds in six out of nine patients. Desensitization also prevented histamine release after skin exposure to cold. Surprisingly, skin histamine levels and release after codeine injection were found to be normal in desensitized patients.