A person with Aquagenic Urticaria is essentially allergic to water. It is an extremely rare condition with no cure.
After coming into contact with water - or blood, sweat and tears - the sufferer develops painful, itchy hives that spread over the affected area. These can last anywhere between 10 minutes to an hour-and-a-half and some sufferers have to lie down to let the pain subside.
The condition, considered a rare disease, mostly affects women and can develop during puberty. The underlying cause is unknown.
There is no proven treatment, so the recommendation is to avoid all forms of water, keeping showers short and avoiding rain.
There is limited data on successful treatments, but for some patients, antihistamines — which are often used to counteract allergic reactions — help. Some other medications, light therapy, and sodium bicarbonate have been found to be helpful as well.
More allergy information and advice here