Water allergy, also known as aquagenic urticaria, is a rare condition where hives develop when the skin comes in contact with water.

Water is an integral part of daily life and generally harmless for most people. However, it can be a source of discomfort and irritation for some individuals.

Urticaria, or hives, can range from a few millimeters (mm) to several centimeters in size and may appear anywhere on the body. In aquagenic urticaria, the hives are usually only 1–3 mm in size. Hives are itchy and may cause discomfort.

Water sources — including sweat and tears — may trigger an aquagenic urticaria reaction. The condition is more common in females, with most cases being sporadic. Some familial cases also exist. However, research into the condition is ongoing.

There are other types of more common urticaria that someone may mistake for aquagenic urticaria, which is a rare condition. These conditions include cold urticaria and cholinergic urticaria, known as heat hives.

This article discusses water allergies in more detail, including symptoms, causes, diagnosis, and treatment. It also answers some common questions about aquagenic urticaria.

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The hives caused by a water allergy can develop within 20–30 minutes of a person’s skin making contact with water.

Other common symptoms a person may experience are:

Some people may also experience rarer symptoms, such as shortness of breath and wheezing. The symptoms generally subside when water is no longer in contact with a person’s skin. It takes approximately 30–60 minutes for symptoms to subside.

The exact causes that lead to water allergy are still unclear. Scientists have proposed several mechanisms that may lead to a water allergy.

Limited evidence suggests that water may dissolve allergenic substances on the skin surface. This may activate allergy cells, or mast cells, either on the skin’s surface or deeper after penetration through the skin’s top layer.

In another proposed mechanism, water may interact with skin oils, or sebum, from the skin’s oil-producing glands to directly irritate allergy cells and cause the release of allergy-related proteins called histamines.

It is important to note that researchers have not widely studied the causes of aquagenic urticaria. Further research into the causes of water allergies is necessary to better understand the condition.

Doctors may perform an initial physical examination of symptoms and review a person’s medical history to diagnose a water allergy.

Healthcare professionals may also conduct a water challenge test to effectively diagnose aquagenic urticaria. This test involves placing a warm — approximately 95°F (35°C) — damp cloth on the skin for around 20 minutes to provoke an allergic reaction. If allergic symptoms arise, it indicates that a person has a water allergy.

The water challenge test also helps to differentiate aquagenic urticaria from other types of urticaria. A cold cloth might provoke cold urticaria, and an overly warm cloth could provoke cholinergic urticaria.

Although there is currently no cure for water allergies, several treatment options are available to alleviate the symptoms. However, it is important to note that due to the condition’s rarity, scientists have not widely studied its treatment.

Common treatment options may include:

  • Oral antihistamines: Since histamine causes several symptoms of aquagenic urticaria, antihistamines may serve as the first line of treatment.
  • Topical therapies: A person applies topical medications to the skin, which absorbs these medications. Oil-based emulsions and petrolatum-containing creams may treat water allergy symptoms in some people.
  • Phototherapy: A doctor may suggest phototherapy if oral and topical treatments do not produce the desired results. Phototherapy involves UV radiation, and a doctor may use it alongside antihistamine therapy.
  • Other medications: Stanozolol, an anabolic steroid, and selective serotonin reuptake inhibitors (SSRIs) may help treat aquagenic urticaria. Doctors may also use an asthma medication, omalizumab, to treat water allergies.

Below are some of the most common questions and answers about water allergies.

What causes water allergy?

The exact cause of water allergies is unknown.

However, some scientists hypothesized that the cause may include the release of histamine by mast cells. This may be due to the formation of a toxic substance, or by a water-soluble antigen and a change in osmotic pressure surrounding hair follicles.

However, sometimes water allergies also arise independently of histamine release.

Can a person suddenly develop an allergy to water?

Researchers have found that water allergies mostly develop during puberty or postpuberty. Researchers have also noted some reports of water allergy developing in childhood.

However, further conclusive research about this rare condition is necessary.

How common is water allergy?

Water allergy is a significantly rare condition. A 2020 study reported approximately 100 cases of aquagenic urticaria worldwide.

Water allergy, or aquagenic urticaria, is a type of urticaria that is caused by skin contact with water. People with the condition develop hives upon contact with water.

A person should speak with a doctor if they believe they have an allergy. Water allergy may have symptoms that overlap with other more common types of hives, such as cold-induced hives known as cold urticaria or heat-induced hives known as cholinergic urticaria. A doctor can help diagnose the type of urticaria and provide treatment.