How skin pigment protects us from UV rays

To protect the body from the dangerous ultraviolet (UV) rays from the sun, skin pigment converts UV radiation into harmless heat through a rapid chemical reaction, a study says.

"In this way, the pigment disarms the energy in the UV light and prevents it causing harmful chemical reactions," said Villy Sundstram, a professor of chemistry at the Lund University in Sweden.

Pigment in skin and hair comprises two different types of melanin: eumelanin and pheomelanin.

Eumelanin makes people develop a sun tan and gives colour to brown and black hair, whereas those with red hair and pale skin have high levels of pheomelanin.

"We found that eumelanin converts harmful UV radiation into heat with almost 100 percent efficiency," Sundstram pointed out.

"The chemical reaction is incredibly quick, taking less that a thousandth of a billionth of a second," Sundstram explained.

What happens in detail in the chemical reaction is that a hydrogen ion - a proton - is ejected from the pigment at the same moment the UV light reaches the pigment molecule.

The chain of events could be likened to the melanin getting rid of the energy of the UV light by shooting a proton projectile very quickly.

This projectile in turn gives off energy to the surrounding membrane tissue in the form of heat, thus converting dangerous UV radiation into harmless heat, the findings showed.

"By understanding how the body naturally protects itself against UV light, we can develop better sun protection products based on the same principles," Sundstram maintained.

"This would provide better protection against skin cancer," he emphasised.

The study appeared in the Journal of the American Chemical Society.