Atopic dermatitis, a long-term type of inflammation of the skin, can significantly raise the risk of developing inflammatory bowel disease (IBD), an intestinal disorder, according to a new study.

The study, published in the JAMA Dermatology journal, showed that while adults with atopic dermatitis have a 34 per cent increased risk of developing IBD, children have a 44 per cent increased risk.

Atopic dermatitis is a chronic disease that causes inflammation, redness, and irritation of the skin. IBD encompasses the diseases ulcerative colitis and Crohn’s disease, which are disorders involving chronic digestive tract inflammation.

While IBD is located in the gut and atopic dermatitis affects the skin, both diseases are driven by the immune system and are categorised by severe inflammation.

"It is imperative for clinicians to understand atopic dermatitis and the trajectory of our patients with it in order to provide the best standard of care," said Joel M. Gelfand from the University of Pennsylvania in the US.

"Atopic dermatitis and IBD can cause changes in the microbiome, chronic inflammation, and the dysfunction in the skin and gut barrier respectively. There are also specific cytokines, certain kinds of proteins, that play a role in immune system activity and that seem to be related to AD and IBD," he said.

The team studied over 1 million children (participants from under 1 year old to 18 years old) and adults with atopic dermatitis. They found that the skin condition was not linked to higher ulcerative colitis in children unless the kids had a severe case of atopic dermatitis.

Children with atopic dermatitis, however, had a 54 to 97 per cent increased relative risk of Crohn’s disease. And among children with severe atopic dermatitis, the risk was roughly five times higher.

In addition, adults with atopic dermatitis had a 32 per cent increased relative risk of ulcerative colitis and a 36 per cent increased relative risk of Crohn’s disease.

"Investigating the relationship between skin diseases and other diseases doesn’t just offer new insight into how these diseases can affect a patient with both, but these studies are especially powerful because they also highlight unique characteristics of each disease and how they behave individually," Gelfand said.