Image caption Nicola Branch says people have made fun of her condition

Official statistics suggest cases of people with an allergy to water are vanishingly rare.

The Anaphylaxis Campaign - an allergy charity - says there are about 35 known cases in the entire world.

And for that reason, scientific understanding of the condition is relatively limited.

Aquagenic urticaria - as it is officially called - is something that even many medical professionals know nothing about.

But after discussing the condition on BBC Radio 2's Jeremy Vine Show, the production team was amazed when dozens of people came forward to say they were suffering in a similar way.

It seemed that thanks to our radio phone-in, we had discovered that more people suffer with an allergy to water than previously thought.

Dr Sarah Jarvis, a GP and BBC Radio 2's medical expert, says: "Allergy to water is remarkably rare.

"Some people are so allergic to water that even their tears or their sweat can cause them to come out in a rash.

"The most common time to develop allergies in general is around the time of puberty, although they can be developed at any stage of life.

"Often the allergy can become worse over time.

"A true water allergy is a type of urticaria.

"With urticaria, within one to 15 minutes of being exposed to a substance, you come up in hives.

"It is like nettle rash on the skin, and you can get really dramatic swelling all over.

"Fingers especially can become red, hot and intensely itchy."

Image copyright CID/ISM/SCIENCE PHOTO LIBRARY Image caption The allergy can cause hives

Dr Jarvis says antihistamine tablets are used to treat most types of urticaria, but they deliver only variable success for those with a genuine water allergy.

"There simply aren't enough people in the world who have it to be able to successfully conduct the studies we need to," she says.

"There is no definitive cure."

But as with any allergy, people who suffer do so with varying degrees of severity.

Dr Jarvis says: "Some people will come out in hives regularly, others occasionally, and some people will get it chronically, with the swelling and itching lasting for weeks."

Below, some of our listeners explain what it is like to be allergic to water.

Nicola Branch, 51, London

Image caption Nicola says a flare-up is like holding a stinging nettle to her face

There have been times where it has felt like someone is holding a stinging nettle to my face.

The allergy - which mainly causes intense itching - is concentrated in the creases of my elbows, the backs of my knees and my face.

Even sweat makes me itch.

I have to carry a hand towel with me everywhere I go to wipe it off.

I am a cyclist, and every time I come to standstill, I dab my face.

Sometimes people do not believe that you are allergic to water; they take the Mickey out of you.

Alan Pywell, 71, Rochdale

It all started when I was about 60.

I was a metal grinder, and initially I thought it had something to do with metal dust getting to me.

If I had a shower or got my hands wet, they - along with my torso and back - would itch like nobody's business.

I get a red rash all over.

If you were to feel my arm after I have a reaction, it feels like sandpaper.

And in fact if someone had rubbed actual sandpaper on me after, it would have been a relief.

The itching is so intense that at times I would actually go outside and rub my back against a pebbledash wall.

I flare up even if I do everyday tasks like cleaning out the fish tank.

If it was much more severe, I can see how it might drive you to suicide.

You just want anything to take the pain away.

I went to the see the doctor, and we went through everything in my lifestyle.

I changed shampoo, shower gels, water temperature, and nothing worked.

My doctor eventually decided that the only thing it could be was water.

I am helped now by a heavy-duty antihistamine.

Noah Auerbach, 30, Manchester

I was eight when it first happened.

I was walking to school one day in the rain, and my hands and neck swelled up with hives - it was really frightening.

I later went to the doctor for an allergy test.

They put tiny drops of different substances on my arm to see what I was allergic to.

They also put a 'control' substance on, which was water.

It is a control substance because water is not supposed to cause a reaction at all.

But after 15 minutes, my entire arm swelled up.

It turns out that I was allergic to it.

It got worse for me.

I would play sport at school - but the moment I started to sweat, I would get swelling.

When the swelling happens around my joints, it really hurts.

When my neck swells up, it makes me wheezy.

Teachers did not believe me when I said I could not play sport in the rain - until they saw what it did to me.

I take antihistamines every day, which means I can drink water - it is a necessary evil.

I tend to have three-minute showers and have to get dry as fast as possible.

From the response we got from our listeners on the Jeremy Vine Show, it would appear that a true allergy to water could be more common than widely believed.

Amena Warner, the head of clinical services for Allergy UK, said: "Once awareness is raised of what the symptoms are of this condition, then many people may associate this with the symptoms they are experiencing.

"And so, we may come to realise that actually it is not quite as rare as we think."