Urticaria is the medical term for the red, itchy, raised rash that most of us call hives. About one-fifth of the population will have hives at some point. It's a common ailment. But one form of hives, called aquagenic urticaria, is a very rare condition.
We only know of about 100 cases of aquagenic urticaria. As you may guess by looking at the name, contact with water causes it. Those with this condition often develop red, itchy skin when they touch water. The temperature and acidity or alkalinity of the water aren't factors in causing a reaction. A few people react only to saltwater.
What Are the Symptoms?
The rash caused by aquagenic urticaria is made of small, raised bumps surrounded by larger, reddened areas. The bumps may itch. They usually appear on the neck, the upper arms, and the trunk.
The rash usually goes away in 30 to 60 minutes. Sometimes the person develops other symptoms, including headache, shortness of breath, wheezing, dizziness, and fainting.
How Is It Diagnosed?
A doctor may suspect aquagenic urticaria when seeing someone who has a history of rash after water exposure. Still, heat, cold, pressure, and other conditions can trigger similar rashes. Part of the doctor's job is eliminating those other causes of rash.
Doctors usually base a diagnosis of aquagenic urticaria on a "water challenge test." The doctor places a wet compress on the person's chest and checks for rash after 20 minutes has passed. It's important that the person being tested does not have any antihistamines in their system. It's also important that the water is not hot or cold.
How Do People Cope With Aquagenic Urticaria?
Being allergic to water presents some challenges in everyday life. You may wonder how people cope. Here are some ways.
Drinking water. People with aquagenic urticaria can often drink water without having a reaction because the water really doesn't touch their skin.
In one case, an 18-year-old male had swelling of the lips and the inside of the mouth after drinking water.
Bathing. Treatment can make bathing and showering less risky. Often those with aquagenic urticaria reduce their frequency of bathing, sometimes using alcohol-based cleaners instead.
Other exposure to water. Those with aquagenic urticaria may react to water in any form, including their own sweat and tears. They often take precautions, such as staying inside on rainy days and avoiding activities that cause sweating.
Treatment for Aquagenic Urticaria
Because so few people have aquagenic urticaria, there is not a lot of interest in finding treatments for it. Those with the condition commonly use two strategies to manage it. Two other methods are possible.
Antihistamines. The usual treatment for hives, no matter what type, is antihistamines. Doctors prefer second-generation antihistamines because they cause less drowsiness than the older formulas. Cetirizine is a frequent choice.
Barriers. Creams and other substances that form a barrier between the water and the skin are also helpful. Some experts recommend that these agents be tried before antihistamines, especially with children who are allergic to water.
Ultraviolet light therapy.Phototherapy using ultraviolet light is a less commonly used treatment. It toughens the skin and makes it less sensitive to water. The idea is to make the skin more like that on the palms of the hands and the soles of the feet, as water rarely causes a reaction in those places.
Omalizumab. Doctors have had some success treating hives with an allergy medicine, omalizumab. One person with aquagenic urticaria eliminated all symptoms and could even go swimming after using this drug. There are some problems with using omalizumab. It is off-label for hives, and it is more costly than other treatments.
Causes and Risk Factors of Aquagenic Urticaria
Doctors often must treat hives without knowing what caused the rash. In chronic hives, they identify only about 10% to 20% of the causes. When the cause is known, doctors may not understand the mechanism that triggers the rash.
Doctors and researchers are similarly puzzled about aquagenic urticaria. They have guessed that something on the skin that reacts with water causes the rash. They have also theorized that a substance dissolved in the water causes the rash and not the water itself. But so far they have not found a definite answer.
There are no known risk factors for aquagenic urticaria. A family may have more than one case, but most cases do not occur in family groups. A few people with the condition have had other inherited conditions. So far, there have not been enough cases for researchers to determine whether the condition might be inheritable or whether it might be part of a larger syndrome.