Aquagenic Urticaria: A Perplexing Physical Phenomenon.

Aquagenic urticaria (AQ) is a rare physical urticaria induced by contact with water. It may be distinctive clinically, evident as 1-2 mm folliculopapular urticaria, a pattern also characteristic of cholinergic urticaria. AQ has a truncal and upper extremity distribution within 20-30 minutes after contact with water, regardless of its temperature or source. AQ is usually symptomatic with mild to severe pruritus and a burning sensation. The mechanism by which water produces mast cell degranulation and histamine release remains unclear. We review its clinical presentation, diagnostic parameters, differential diagnosis, and treatment.