Meet Harry, the little boy who's allergic to WATER

For most children, bath time is fun. But four-year-old Harry Floyd used to have a very different experience; soon after climbing into the water he became covered in an angry, itchy rash across his body.

He suffers from physical urticaria, essentially a skin allergy to a host of seemingly benign triggers including water and hot or cold weather.

Recent research, published in the Expert Review of Clinical Immunology, suggests around 100,000 Britons suffer from the condition, although experts say this may be an underestimate, with many more going undiagnosed.

The condition means patients develop a rash of small, incredibly itchy bumps (urticaria means hives) in response to a range of unusual and diverse triggers.

Many are allergic to weather, and develop hives in hot and cold temperatures, while others break out in response to exercise, or even pressure on their skin such as a bag

on their shoulder or even a tight bra strap. More rarely, some people with physical urticaria develop the rash in response to water, or even sunlight.

However, in many cases, especially where the symptoms are not severe, people think they have reacted to something they have eaten, or have used on their skin.

The hives are triggered by the chemical histamine, which is released in the body during an allergic reaction.

The problem can start at any age. Harry first started to develop rashes at three months old, says his mother Lisa, a 39-year-old GP practice manager. 'The first time it happened he woke at 3am covered in the rash and screaming,' she recalls. 'But it cleared up within an hour, so by the time we got him to the doctor there was nothing to see.

'We initially thought it was the soap or shampoo he was allergic to, but even when we just used water to bathe him he would still get the rash.' He also got a rash round the waistband of his nappy.

Lisa was then alarmed to see something as innocuous as bad weather would trigger a rash. 'When the weather was really cold he'd start to get a rash within a few minutes that would spread over his body.

'He would also get the rash in hot weather. He'd just scream and try to scratch it.'

The family took Harry to the doctor multiple times over the next year, but were told it was simply a virus (the condition didn't affect his older brother, Oliver, now six). At six months Harry was diagnosed with multiple food allergies, including to egg and dairy, which doctors thought might have triggered the rash. But he continued to get the rash even after avoiding those foods.

Out of desperation, Lisa and her husband Eddie, 66, who live in Walsall, West Midlands, took Harry to Great Ormond Street Hospital in London where they paid to see a private specialist - and Harry was diagnosed with physical urticaria.

Read more: Here