Blood histamine levels following graded cold challenge in atypical acquired cold urticaria.

Acquired cold urticaria with a negative cold stimulation test has been described in seven patients in whom the standard ice cube test did not induce localized urticaria. Subsequent total body cold exposure induced a generalized urticaria. A patient with this syndrome is presented where blood histamine levels rose from 9 to 60 micrograms/dL after a negative local cold stimulation test and from 60 to 90 micrograms/dL after total body cold exposure. Urticaria occurred only after generalized cold exposure. Blood histamine levels following the ice cube test may represent a sensitive method to diagnose this form of atypical acquired cold urticaria, without subjecting the patient to the risk of anaphylaxis reported following total body cold exposure.