Allergic skin condition and cancer

People with atopic dermatitis, an allergic skin condition, have a higher risk of getting cancer.

Atopic dermatitis is a type of eczema, or skin inflammation that arises from an allergic reaction. It causes itchy rashes that get crusty and scaly with scratching. There have been conflicting theories about whether these kinds of frequent rashes that drive the immune system into action would make it more or less likely for someone with atopic dermatitis to develop cancer.

To investigate, researchers analysed the medical records of about 4.5 million people in the UK and followed their medical history for an average of almost 7 years. About 1.5 percent of those individuals had atopic dermatitis and just under 3 percent were diagnosed with some kind of cancer during the study period. People in the study with atopic dermatitis were on average 12 to 15 years younger than those without atopic dermatitis.

Overall, people without atopic dermatitis were more likely to get cancer than people with the skin condition. There were 129,272 first cancer cases in people without atopic dermatitis (about 33 cases per 10,000 persons per year) and 700 first cancer cases (about 42 cases per 10,000 persons per year) in those with atopic dermatitis. But when the investigators took into account the effect of age differences and looked within each specific age group, the pattern changed. At every age, the rate of cancer was higher among patients with atopic dermatitis.

This general pattern held when the researchers looked specifically at lymphoma, melanoma, and non-melanoma skin cancer. People with atopic dermatitis are about 1.5 times more likely to be diagnosed with some kind of cancer than people without atopic dermatitis.