Sunburn & Immunity

Researchers at the Melanoma and Skin Cancer Research Institute (MASCRI) at Australia's Royal Prince Alfred Hospital in Sydney have recently reported the results of a new study examining whether sunscreens offer protection against the harmful effects of ultra violet (UV) radiation on the skin's immune system.

It has been known for more than 20 years that UV radiation can suppress the function of the skin's immune cells, by inactivating and depleting Langerhan's cells in the skin, and although these immune cells appear to recover their function two to four weeks after the UV exposure, repeated exposures can result in chronic immunosuppression. The immune system is an important line of defence against melanoma and other skin cancers and it is believed that UV immunosuppression may result in an increased risk of these skin cancers. Dr. Diana Damian, Dr. Gary Halliday and Professor Ross Barneston have developed a simple and effective method for measuring immune responses in the skin of human subjects.

The study found that even relatively small doses of ultraviolet radiation caused significant immunosuppression in the skin of volunteers. Using less UV than is needed to cause mild sunburn, once daily for five days, the skin's immune responses were reduced by an average of 40%. Interestingly, individuals with darker skin were just as easily immunosuppressed as those with very pale skin.

"Ultraviolet radiation exposures here are higher than almost anywhere else in the world, due to our climate, our latitude and the ongoing depletion of the ozone layer."

The "Journal of the American Medical Association" warns that, as well as causing skin cancer and cataracts, even a slight case of sunburn suppresses immune-system protection against a variety of infectious diseases.

These include tuberculosis, leprosy, malaria, measles, chicken pox, herpes and fungal diseases.

There are also fears that vaccination programs could be compromised.

Research shows that too much ultra violet radiation changes the behaviour of the immune cells which operate directly under the skin layer.

Immune cells which normally would repel infections coming in contact with the skin, slow their actions which makes it easier for an infection to become established.