What distinguishes Aquagenic Pruritus (AP) from Aquagenic Urticaria (AU)?

AP is characterized by a severe prickling-like sensation or itch, but the skin appears normal during the itchy period, unlike AU.

Aquagenic Pruritus (AP) and Aquagenic Urticaria (AU) are two distinct, though related, manifestations of water sensitivity. While both are triggered by contact with water, AU is defined by the physical symptom of developing visible hives or swelling (urticaria). In contrast, AP is characterized solely by an intense sensation—a severe prickling feeling or itch—without the accompanying development of visible dermatological changes like hives or blisters on the skin surface during the itchy episode. Although the underlying etiology remains undetermined, potentially involving mast cell degranulation, the absence of visible skin lesions is the critical clinical differentiator between AP and the hive-forming AU.