Dissociation of histamine release and clinical improvement following treatment of acquired cold urticaria by prednisone.

1 Corticosteroids are known to suppress evoked histamine release from human skin in vitro. Therefore the effect of prednisone, on cold evoked histamine release and clinical response was studied in six patients with acquired cold urticaria. 2 Following cold challenge all six patients developed an immediate urticarial response of the forearm and elevation of histamine levels, measured by superfusion cascade bioassay of the venous blood draining the forearm. 3 After treatment with prednisone, in an oral dose of 20-25 mg for 1 to 5 days, a suppression of evoked histamine release occurred in all but one patient. However, there was no corresponding decrease of erythema or oedema, though pruritus was improved in most patients. 4 The lack of clinical improvement in erythema and oedema, despite reduction in histamine levels, suggests that histamine may not be the principal mediator of the vascular response to cold challenge in acquired cold urticaria.