New light on skin cancer mechanisms

Ultraviolet light may cause immune system suppression. UV radiation studies found that urocanic acid present in the outer layer of skin appears to control the immune response of skin cells burned by the sun. The immune system initially reacts against burned skin cells. Urocanic acid probably then shuts off the assault to prevent the body from attacking its own tissues. But if skin cells become overly sunburned and a malignancy forms, the cancer cell is not attacked by the immune system because urocanic acid has shut off the immune response, allowing the tumor cell to survive. Because of these studies, most sunscreens no longer contain urocanic acid. Eating habits and genetics may also contribute to skin cancers and melanomas caused by excessive exposure to the sun.