Most people are well aware of the risks from remaining unprotected from the effects of the sun while they are sunbathing, with the rise in cases of skin cancer a common topic in the news during the summer months. Recent scientific research suggests though that the risk can be just as real in the dark, in fact it seems that most of the damage caused to the skin occurs when it is dark, which seems to be contrary to what most people have long believed.

The findings by a team from Yale come hot on the heels of the recent news from Cancer Research UK, whose own analysis suggested that one in two people in the UK will be diagnosed with some form of cancer during their lives, a frightening statistic to be sure.

The scientists from Yale began with the basic notion that DNA in melanocytes (cells that make up melanin, the pigment that is the primary determinant of skin colour) is damaged by exposure to ultra-violet rays. Excessive exposure leads to the commonest form of skin cancer in America.

Contrary to the view held in the past that melanin can act as a shield to protect the skin against UV rays, the research concluded that it is actually linked with damage to skin cells. Their tests suggested that it could actually work both ways, acting to fight cancer but also to assist in its creation. Part of the team doing the research, Douglas E. Brash (a professor of therapeutic radiology and dermatology) suggested that "melanin does protect against CPDs" and that it "does act as a shield" but it "is doing both good and bad things."

Cyclobutane dimer (CPD) is the name given to the DNA damage that is done, which commonly results in two 'letters' of a DNA strand becoming entangled together, thus stopping genetic information from being read as it usually would.

The Yale team found that cell degeneration continued to take place hours after UV exposure (with melanin in the cells), but that in cells without melanin they were only affected by CPD while they were exposed to UV. Seeking confirmation of their findings, Brash and the rest of the team experimented with mice and concluded that half of the melanocytes that they saw were created during the dark, after exposure.

In attempting to explain their findings, Sanjay Premi, an associate on the research, determined that in reaction to UV rays two enzymes combine and this causes the "exciting" of an electron in melanin. The energy created by the process is known as chemiexcitation, which only happens in the dark. Scientists have been aware of chemiexcitation for some time, but only in lesser animals and lower plant life, not in humans.

Since the process occurs after something that has happened before though, it can be mitigated against. The Yale scientists observed that this can be achieved through the application of special lotions that are specifically aimed at preventing chemiexcitation from occurring.