Sunlight ‘continues to damage skin for hours after exposure’

The damage that ultraviolet (UV) radiation causes to skin can continue hours after sun exposure, according to new US research.

A team from Yale University made this discovery after exposing mouse and human melanocyte cells to UV radiation, finding that it cause a form of DNA damage called cyclobutane dimers (CPDs) not just immediately, but also for a number of hours after UV exposure ended.

This longer-term effect did not occur when the cells did not possess melanin, the pigment that gives the skin its colour and is also known to offer protection against UV radiation in most cases.

It was shown that UV light activated two enzymes that combined to excite an electron in melanin, giving rise to a process called chemiexcitation that causes DNA damage.

Douglas Brash, clinical professor of therapeutic radiology and dermatology at Yale School of Medical, said: "If you look inside adult skin, melanin does protect against CPDs. It does act as a shield. But it is doing both good and bad things."

It is hoped that this research could lead to the development of additional preventive tools, such as an evening-after sunscreen, to combat skin cancer on a new front.