Evaluation of a patient with both aquagenic and cholinergic urticaria

An 11-yr-old girl presented with a history of urticaria induced by warm or cool showers, exercise, and emotional stimuli. During evaluation she repeatedly developed generalized punctate urticaria, pruritus, palpitations, and headaches after warm baths or exercise, and she had a positive methacholine skin test. She developed similar lesions and pruritus after local application of sterile water, tap water, ethanol, normal saline, or 3% saline. The diagnosis of combined aquagenic and cholinergic urticaria was made and presented a unique opportunity to study and compare mediator release and clinical symptoms in both conditions. The patient was submerged in bath water at either 37° or 41° C to induce either aquagenic or cholinergic urticaria, respectively. Histamine was released into the systemic circulation in both condition in a similar time course; however, systemic symptoms occurred only after the 41° C bath. After failure to induce tolerance to the 41° C bath water, hydroxyzine therapy was instituted. One week later she was rechallenged; few symptoms appeared, and a rise in serum histamine was not detected as had been shown in previous challenges. The data suggest that in our patient, hydroxyzine may have contributed to the inhibition of both histamine release and the appearance of symptoms during hot bath challenging.