The number of young people admitted to hospital with Crohn's disease in England and Wales has soared, figures show.
The disease mainly attacks the intestine and can result in severe diarrhoea, cramps and tiredness.
The Health and Social Care Information Centre says 4,937 16 to 29-year-olds were admitted for treatment in England in 2003/4. Last year it rose to 19,405.
It's estimated around 250,000 people suffer from the condition in the UK.
One expert says she and her colleagues are investigating whether junk food and too many antibiotics could be behind the rise in some cases.
The exact cause of Crohn's disease is unknown. However, according to NHS Choices, a combination of factors may be responsible.
* Genetics - genes that you inherit from your parents.
* The immune system - a problem with the body's defence system against infection and illness.
* Previous infection - this may trigger an abnormal response from the immune system.
* Smoking - smokers with Crohn's usually have more severe symptoms than non-smokers.
* Environmental factors - Crohn's disease is most common in westernised countries such as the UK, and least common in poorer parts of the world such as Africa, which suggests the environment has a part to play.
There is no cure for Crohn's but many patients learn to manage the symptoms, often by altering their diet.
The disease can be found anywhere along the gastrointestinal tract from the mouth to the anus.
The walls of the tract become inflamed, often ulcers can develop and they can be painful as food passes them in the intestine.
Similar figures released to Newsbeat by NHS Wales Informatics Service also show a rise there.
In 2003/4 Welsh hospitals admitted 277 patients for Crohn's disease. That rose 114% to 594 last year.
Liam Ruff, 19, was diagnosed with Crohn's when he was 12.
"When I was 17 I had an operation for something called an ileostomy," he recalls.
"That's part of my intestine coming out of my tummy.
"For a whole year I lived with that hanging out of my tummy with a bag attached to it. So anything that passed through me was collected in that bag and then I'd empty the bag."
He says it was "very tough" and feels he's missed out on things many people take for granted like playing sport and drinking alcohol.
"I have had a bit of depression with it. There are odd days when I have a little cry, and then just get on with it," he says.
Today Liam says he still suffers from severe diarrhoea.
"It's certainly embarrassing when I'm in a public place," he says.
"If I go to a concert, the first thing I look for is the nearest toilet. That's not what regular people do.
"By the time you do the things you normally would do, like work, college or school, you are worn out completely."
Dr Sally Mitton says she and her colleagues at St George's Hospital in Tooting, south-west London, have seen a rise in the number of young people with Crohn's.
"We try to keep patients fit enough so they can stay at home but because of the increased overall number being diagnosed, the actual number needing to be admitted [to hospital] has gone up," she says.
"We know that there are many genes that predispose someone to get Crohn's disease.
"But we also know that lifestyle factors like eating a lot of junk food or taking many courses of antibiotics may make it more likely to happen."
The charity Crohn's and Colitis UK says most sufferers find fatigue the hardest symptom to handle or get treatment for.
After four years of research they are launching a new questionnaire to help quantify tiredness.
Prof Chris Norton from King's College London led the project.
She says it will help doctors establish what treatment will work best.
"Young people have told us that it really impacts their education, their social lives and their ability to get and hold down a job," she says.
Crohn's affects the immune system and is therefore medically an autoimmune disorder, which means the body produces antibodies that work against itself.
Other autoimmune disorders include rheumatoid arthritis, ulcerative colitis, psoriasis, psoriatic arthritis, ankylosing spondylitis, lupus, and Graves' disease.
Following the original story and subsequent coverage elsewhere Dr Sally Mitton clarified some of her comments:
"Since the initial report on 18th of June there have been subsequent newspaper and television reports that focus on the assumption that Crohn's Disease seems to be "caused" by junk food and multiple antibiotics. This is not my belief and is a distortion. I did not mean to imply any element of self-infliction and I am appalled to think this could set back public perception of IBD or that sufferers might be blamed for their own pain and misfortune. I would like to sincerely apologise for the distress that my comments have caused."