The risk of melanoma is up to 50 per cent lower in people with atopic disease than controls, a new study from Finland reports. Atopic people also show a lower risk of other malignancies.

Researchers enrolled 250 males and 246 females aged 21-79 years at high risk of skin cancer (e.g. past or present skin cancers or actinic keratosis, atypical moles, skin phototype or immunosuppression). 

No association emerged between atopy and photodamage, basal cell carcinoma or nevus (mole) count but 14.6 and 22.2 per cent of atopic and non-atopic patients respectively had past or present melanoma. 

Allowing for confounders, atopy reduced melanoma risk by 42 per cent. In addition, 5.8 and 11.1 per cent of atopic and non-atopic patients respectively had past or present squamous cell carcinoma, although this difference was not statistically significant. Of the atopic and non-atopic patients, 8.8 and 15.7 per cent respectively developed malignancies other than skin cancer. 

After allowing for various confounders, atopy reduced the risk of non-skin cancer malignancies by 51 per cent. 

“The latest theory is that the skin has a naturally occurring autoreactive immunoglobulin E [IgE] response that could protect against carcinogens and skin damage leading to cancer. This theory makes sense because atopic diseases typically involve an IgE-mediated allergy, so the protective mechanism may be even more pronounced in atopic skin,” says Professor Ilkka Harvima from the University of Eastern Finland and Kuopio University Hospital. 

Professor Harvima and colleagues are now analysing skin biopsies taken during the study to explore the underlying cellular mechanisms. (Melanoma Res DOI: 10.1097/CMR.0000000000000887)