• A substance dissolved in water enters the skin and triggers an immune response. In this theory, the hives are not caused by water, specifically, but rather an allergen in the water.
• An interaction between water and a substance found in or on the skin generates a toxic material, which leads to the development of hives.

Due to the rarity of aquagenic urticaria (AU), there is very limited data regarding the effectiveness of individual treatments. To date, no large-scale studies have been conducted. Unlike other types of physical urticaria where one can avoid the agent that causes the hives, avoidance of water is not practical. The following treatments (alone or in various combinations) have been used to manage or treat AU with variable results:

• Antihistamines – These typically are used as the first-line medical therapy for all forms of urticaria. Those that block H1 receptors (H1 antihistamines) and are non-sedating, such as cetirizine, are preferred. Other H1 antihistamines (such as hydroxyzine) or H2 antihistamines (such as cimetidine) may be tried if H1 antihistamines are not effective.
• Creams or other topical agents that serve as a barrier between water and the skin, such as petrolatum-based products. These may be used prior to bathing or other exposure to water to prevent water penetration into the skin.
• Ultraviolet light therapy (also called phototherapy), such as Psoralens ultraviolet radiation A (PUVA) and ultraviolet radiation B, have been reported to resolve symptoms of AU in a few cases.
• Omalizumab – an injectable medication typically used for people with severe asthma. This medication has reportedly been tried successfully in a few people with AU.

Due to the lack of strong evidence of the safety and effectiveness of the treatments mentioned above for people with AU specifically, those with AU should consult with their doctors regarding personal treatment options. Some people with AU may not experience improvement of symptoms with medical treatment and may need to rely on minimizing water exposure by limiting bathing time and avoiding water-based activities.