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Water is an inevitable necessity to living being. Yet, for certain individuals, water isn't a definitive refreshing liquid, it can really be impeding to their wellbeing. Aquagenic urticaria is a rare physical urticaria that occurs upon cutaneous contact with water. Nearly about 50 cases have been reported so far. The World Allergy Organization guidelines on urticaria now classify AU as an inducible type of chronic urticaria, whereas this condition and other physical urticarias were previously grouped together due to their inducible nature by specific physical stimuli. It is more predominant in females than males during puberty or post puberty and a few reported childhood onset of disease. Most instances of aquagenic urticaria appear to happen sporadically in individuals with no family background of the disease. No specific gene or locus for AU has been identified. AU has also rarely been reported in association with systemic conditions, including HIV infection, and occult papillary carcinoma of the thyroid gland.

The specific reason for aquagenic urticaria is inadequately perceived. Be that as it may, researchers have proposed various mechanisms. A substance broke down in water enters the skin and triggers a resistant reaction. In this hypothesis, the hives are not brought about by water, explicitly, yet rather an allergen in the water. The pathophysiology is associated with release of histamine by mast cell degranulation, induced by toxins produced by reaction of sebum or sebaceous gland with water. Another proposed mechanism is indirect provocation of urticaria by osmotic pressure changes around hair follicles. An alternative cause known is histamine release induced by presence of water soluble antigens in epidermis.

Clinical manifestation is formation of hives may occur which are approximately 1-3 mm folliculocentric wheals and surrounding 1–3 cm erythematous flares within 30 to 60 minutes after exposure to water. The rashes most commonly affect the neck, upper trunk and arms, although it can occur anywhere on the body. Some may develop itching, pruritus, burning, prickling and systemic symptoms like shortness of breath and wheezing. The lesions generally fade within 30 to 60 minutes after water content is removed. The hypersensitivity response may vary with nature of water to most individuals. Urticaria occurs due to tap water, sea water, tears or sweat, and certain individuals possess difficulty in drinking water. The diagnosis is made by "water challenge test" done by applying a water compress of 35˚C on the upper body for 30 minutes. The patient should be devoid of antihistamines for several days before the test and the serum immunoglobulin E should be within normal level.

Treatment of choice is first-generation H1 antihistamines and H2 antihistamines. 180 mg fexofenadine daily can prevent the wheals and erythema. Treatment with 5 ml ketotifen syrup twice daily is given for improvement of symptoms in children. Acetylcholine antagonists, such as scopolamine is used as an adjuvant therapy with antihistamines. Phototherapy by application of UV light induces epidermal thickening, leads to decreased water penetration and decline mast cell activity. Stanozolol has been reported to control systemic symptoms of aquagenic urticaria.Omalizumab has been successfully applied in a patient to treat urticaria refractory to antihistamines. Petrolatum-coating can act as barrier between skin and water. Precautions should be taken by patients by taking brief, infrequent showers, wearing moisture-wicking clothes, and avoiding rainy day travelling. Complications like scarring and ulceration may further develop by prolonged itching. Patients may suffer from psychological stress due to hydrophobia and this dermal disease negatively impacts patient’s quality of life.