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When you're allergic to water, walking in the rain is miserable

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People with water-caused hives can drink liquids because the allergic reaction occurs only when the outer skin contacts water.

A few years ago, Dr. Alan Baptist, associate program director for allergy and immunology at the University of Michigan, faced one of the toughest allergy cases imaginable.

A young woman came to seek his help with migraine-like pain. Every time she came into contact with water she suffered headaches, along with reddish welts on her skin.

It turned out she was allergic. To water.

If you were allergic to water, how could you bathe? Or swim? A walk in the rain could turn into a painful afternoon. Yet some people truly are allergic to water, suffering with a condition known as aquagenic urticaria, or water-caused hives. The severity of the allergy varies widely, from barely noticeable to severe.

Aquagenic urticaria, first described in 1964, is very rare, although Baptist thinks it may be seriously underdiagnosed. “If a person showers every day and has urticaria every day, their doctor would think they just have chronic urticaria. Even many allergists aren’t going to be familiar with it.”

The body’s rejection of water is wildly counterproductive, mainly because we are made up mostly of water, our cells are filled with it and we can’t live without it. However, in almost all cases, the allergic reaction is ignited only when the outer skin contacts water. That’s how people with aquagenic urticaria can drink liquids and don't have an adverse reaction to their own cells.

But they can be allergic to their tears if they cry, and even their own sweat, Baptist explained. Fortunately, sweat typically doesn’t cause nearly as strong a reaction as diving into a pool.

Patients can be allergic to saliva, too. While a simple peck on the cheek or lips shouldn’t be much of a problem since symptoms generally depend on dose, you could pay a high price for very passionate kissing.

“Bathing is the biggest thing,” Baptist said. “Our patient tried to take very short showers and then dry off very quickly, but she still got the headaches, so she began showering only once every three days.”

It’s unclear what causes aquagenic urticaria and its source hasn’t been pinpointed. Because an outbreak releases large amounts of histamine, the mast cells involved in the body’s inflammatory response seem to be activated. How they are activated is still a mystery. The neurotransmitter acetylcholine is also released, so the nervous system must be perversely triggered, Baptist said.

Those facts point to treatment. While some have tried desensitization therapy – similar to how allergists sometimes treat kids allergic to peanuts -- results have been mixed. Baptist used a tool chest of drugs, including antihistamines and anti-cholinergic medications. Those didn’t suppress the patient’s headaches, so he added SSRI drugs typically used against depression.

“That got the headaches under control,” he said. “And we got the skin under control.”

She wasn’t cured of the allergy, but at least she can shower when she wants.

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