Chances are you or someone you know is affected by allergies. You can be allergic to just about anything – ragweed, grass, pollen, peanuts… you can even be allergic to the cold.
But did you know that you can be allergic to water? That’s right – water.
Tessa Hansen-Smith is a 21-year-old college student in California, and she suffers from a rare condition known as Aquagenic urticaria (AU) .
She started exhibiting symptoms of the condition when she was just eight years old. She would break out into a rash every time she bathed or showered, so naturally, her parents assumed she was having an allergic reaction to a soap or shampoo. After eliminating every possible culprit from their home, Tessa’s mother, who is also a family medicine doctor, knew something else must be causing her daughter’s breakouts .
It wasn’t until two years later that she finally determined that Tessa was suffering from AU. 
What is Aquagenic urticaria?
Aquagenic urticaria is a condition in which urticaria (a.k.a. – hives) develop very quickly on your skin after you come in contact with water of any temperature . This includes tap water, rain, sweat, and even your own tears .
“It’s a really difficult condition to have as I’m even allergic to my own tears, saliva, and sweat,” said Hansen-Smith. “I’m really prone to heat exhaustion and have to avoid physical activity.” 
The condition is extremely rare and only affects one in every 230 million people .
The main symptom of Aquagenic urticaria are hives, which are typically small, skin-colored or red welts. These welts are called wheals, and have clearly defined edges. The most common areas for this rash to develop are the neck, upper torso, and arms, and can often be quite itchy .
There are other symptoms, however, that are associated with the condition.
“I suffer with a lot of muscle fatigue and nausea too,” Hansen-Smith said. “The sickness is usually caused by me eating something with a lot of water in foods like some fruits and vegetables. Even drinking water can cause cuts on my tongue.” 
Tessa cannot play sports, and she needs to be driven around her university campus in order to avoid sweating. The 25-year-old has to limit her showers to only twice per month .
Although rare, there have been other reported cases of Aquatic urticaria. In 2016 the BBC reported on a woman named Rachel Warwick, who is also allergic to water .
Any contact with water leaves Rachel with an itchy, painful rash that can take several hours to clear up.
“The reaction makes me feel as if I’ve run a marathon. I feel really tired afterwards so I have to go and sit down for quite a while,” she says. “It’s horrible, but if I cry my face swells up” .
How Can You Be Allergic to Water?
Water is essential for life, so how can you be allergic to something so essential to your survival?
While there have been a few theories tossed around by scientists, no one really knows what causes the condition. At one point, scientists thought that it had to do with the bacteria on your skin.
The theory was that when water came into contact with the oily components of your skin, it caused them to release toxic compounds that initiated an immune response . It appears though that even after removing the upper layer of skin completely, the reaction continues as normal, rendering this theory incorrect.
At this point, two main theories exist
1) A substance found in water enters through the skin and triggers an immune response. With this theory, the hives wouldn’t be triggered by the water it’s self but a substance in it .
2) Something on or in the skin reacts with water causing it to produce toxic substances that in turn cause the production of hives .
In the case of most allergies, avoidance is the first measure of protection. This, however, is highly impractical and at times impossible for people who are afflicted with the condition. There have been a variety of treatments used for AU with varying levels of efficacy .
Antihistamines are generally the first line of defence, however over time they can become less and less effective .
“To help the rashes, I’d take an allergy tablet, which got rid of them, but aquagenic urticaria gets worse with age, so that no longer works for me like it did,” said Hansen-Smith. 
In some cases, an epi pen may be required if the patient has trouble breathing when they experience a flare-up .
One Promising Solution
There has been one potential solution that is showing some promise – a drug called Omalizumab . Researchers at the European Centre for Allergy Research Foundation in Berlin thought that IgE, the antibody responsible for true allergies might be behind these reactions.
“Instead of reacting to something from the outside world, they’re producing IgE in response to something within themselves,” they said .
Omalizumab was available as a treatment for asthma, and although not an allergy treatment, they put it to the test. Their first trial was with a woman who had a form of urticaria that was triggered by pressure .
The trial was very successful, however there was just one problem – the drug was being used “off-label”. The effectiveness of the drug against urticaria has to be demonstrated in a large-scale clinical trial for it to be approved for use and for insurance companies to cover the one thousand euro-per-month price tag. Of course with it being such a rare condition, finding enough participants for a trial is extremely difficult .
Living With AU
Unfortunately, since there are very few treatment options available for the condition, those who are afflicted have to find ways to live with it.
For Rachel, that means only showering once per week, wearing light clothes and avoiding exercise to minimize sweating, and of course staying inside when it rains. She also drink a lot of milk, since her reaction to it is not as bad as pure water .
For Tessa, it’s about staying positive.
“I try my best to take things one day at a time because some days are better than others,” she said. “If I’m able to see my friends and loved ones without having to leave early due to feeling sick or make it to all my classes in one day, I see that as a win in my book.”