A lot of things people are allergic to things they can actively avoid, but what do you do if you're allergic to water?
Water is a vital part of living, and humans can only last around three days without it - something which causes an issue of Tessa Hansen-Smith, who is allergic to H2O.
Tessa suffers with Aquagenic Urticaria; an extremely rare condition which is thought to affect less than 250 worldwide.
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It's described as 'a rare form of physical urticaria in which hives develop on the skin after contact with water, regardless of its temperature'.
In addition to drinking water, there's all the issue of bathing as well as that (obviously) involves water too.
With the rarity of her condition in mind, Tessa, 25, documents her life on social media and has shared how she gets around the issue of drinking and washing in water in particular.
When someone asked her on Instagram how she's able to hydrate properly, Tessa explained: "You do need [water] to survive, and luckily my immune system doesn't detect every molecule, so I'm able to get some water in from milk mostly."
She also added that she can get some hydration benefits from fruits and vegetables if she eats them with a glass of milk or with high-protein foods.
"I still have to eat a very limited amount," Tessa went on.
"My hands, lips and tongue show how dehydrated I am. My body has just become used to being dehydrated."
In regards to showering, Tessa tries her best to keep herself as clean as possible so she doesn't have to bathe too often.
"I don’t do a whole lot that makes me very dirty, because I can’t," she previously explained to People.
"Standing in a shower for more than five minutes while also trying to not pass out as I hyperventilate while there’s water hitting me, is not a relaxing self-care experience like it can be for others."
Tessa has previously described her condition as 'isolating' as, in summertime in particular, she isn't able to go out and do what most people her age do.
She told ABC News: "In the summertime, when people are going to the beach, people are having pool parties, and trying to escape the heat the best they can, and those are things I can't participate in and can't enjoy, so it can be really isolating."
Sadly there's no current cure for Aquagenic Urticaria so, as well as avoiding water where she can, Tessa takes antihistamines to alleviate the rashes, hives and itching from contact with water.
Niamh Shackleton