Last updated:
12/5/2024
Years published: 2024
NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for the preparation of this report.
Summary
Aquagenic urticaria is an extremely rare type of physical urticaria. It is also considered a form of chronic inducible urticaria, triggered by contact with water regardless of temperature. It is characterized by itchy welts (hives) that develop shortly after exposure and typically resolve within an hour or two 1,2,3,4 .
Although the cause is not fully understood, researchers think it may involve a hypersensitivity reaction between water and certain substances in or on the skin 1,2,4 .
Diagnosis involves a water challenge test and treatment includes medication such as antihistamines, topical barriers such as creams and lifestyle adjustments to avoid triggers 1,2.
In aquagenic urticaria, hives appear rapidly after direct contact with various sources of water (for example, distilled, tap or saline) regardless of the temperature of the water.
The lesions of aquagenic urticaria are characterized by small, punctate (1 to 3 mm), welts that may occur on all parts of the body, although generally not on the palms of the hands and soles of the feet. Welts appear rapidly within 20 to 30 minutes following exposure to water. Once the water source is removed from the skin, the welts generally fade within 30 to 60 minutes.
Systemic symptoms are rare but have been reported and may be induced by either exposure of the skin to water or by drinking water. Some people do not have any reaction for several hours after an attack. Repeated, short, purposeful exposures to water can lead to a lack of an allergy reaction. Aquagenic urticaria is occasionally associated with other forms of inducible urticaria 4. Aquagenic urticaria presents with specific symptoms after water exposure:1,2,3,4
Activities such as bathing, swimming, exposure to rain, sweating, or even tears can provoke symptoms.
Unlike other urticarias, aquagenic urticaria rarely causes systemic reactions like anaphylaxis, also known as anaphylactic shock or allergic shock, a severe, life-threatening allergic reaction that can occur within minutes of exposure to an allergen.
The exact cause of aquagenic urticaria remains unclear. However, several mechanisms have been proposed:1,2,3
Aquagenic urticaria is extremely rare. Fewer than 100 cases have been documented worldwide, making aquagenic urticaria one of the rarest types of inducible urticaria 2,3. Symptoms usually appear during adolescence or early adulthood. It affects males and females equally 3.
Diagnosis can be suspected in people who develop urticaria from water exposure. The diagnosis is confirmed by a water challenge test.
The water challenge test is done by applying distilled or tap water to the skin for 15–30 minutes. The appearance of hives after the water is removed and the skin dries confirms the diagnosis.
The standard test for aquagenic urticaria is the application of a towel of 35°C (95°F) water or physiologic saline to the upper body for 30 to 40 minutes. The challenge is considered positive if urticaria are present at the test site 10 minutes after removal of the towel/compress 4.
Although water of any temperature can provoke aquagenic urticaria, using ambient-temperature water avoids confusion with cold-induced or local heat urticaria. The upper body is chosen because other areas, such as the legs and arms are affected less commonly in aquagenic urticaria. The affected person should avoid taking antihistamines for several days before doing the test 4.
In some people, rinsing specific areas of the body with water or giving a direct bath and shower have been attempted for diagnosis. Use of these approaches may be required when localized testing using a small water compress is negative, although it should be avoided in people who had severe systemic symptoms in the past.
Treatment
There is no cure for aquagenic urticaria but several strategies can help manage symptoms:
Patients should be educated about their condition, triggers and the importance of carrying antihistamines for prompt treatment of symptoms.
Aquagenic urticaria is typically chronic but usually does not tend to worsen over time. Proper management allows most patients to maintain a good quality of life. In rare cases, symptoms may spontaneously improve 2,3.
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