Critical temperature threshold measurement for cold urticaria: a randomized controlled trial of H(1) -antihistamine dose escalation.

Cold urticaria is a rare but severe and potentially lethal condition. It is primarily treated symptomatically with H(1) -antihistamines. However, patients have a variable response to these drugs and, to date, it has not been possible to predict readily the response to therapy of individual patients. To assess the severity of the cold urticaria in naive patients and the response to therapy of patients treated with increasing doses of an H(1) -antihistamine by measurement of critical temperature thresholds (CTT) for producing weals on the forearm. This was a two-centre, hospital-based, double-blind, randomized, parallel-group study of patients with a confirmed diagnosis of cold urticaria of at least 6 months' duration. Patient groups received either a constant dose of desloratadine 5 mg daily for 6 weeks (n = 13), or escalating doses of desloratadine: 5 mg daily for the first 2 weeks, 10 mg daily for the second 2 weeks and 20 mg daily for the final 2 weeks (n = 15). Only one adverse event that appeared to be drug related was reported: mild fatigue after treatment with desloratadine 10 mg that lasted for about 3 weeks and resolved at the end of the study. The desloratadine 5 mg daily dose produced a submaximal reduction of mean CTT which remained relatively constant over 6 weeks. Dose escalation increased efficacy, the reduction in mean CTT at four-times the standard daily dose being significantly greater (P = 0·03) than with the standard dose. Individually, no patient became symptom free (CTT < 4 °C) on 5 mg, while two became symptom free on 10 mg and a further three on 20 mg desloratadine daily. Measurement of CTT allows for individualized risk management and therapy in patients with cold urticaria.