All-over tan is 'impossible to perfect'

Scientists at the University of Edinburgh found that some areas of the body are much more resistant to tanning than others.

They said their findings could explain why some people find it so hard to achieve a consistent tan all over their bodies.

The researchers carried out the study to find out why different types of skin cancer tend to be found in different parts of the body, even though all are caused by exposure to harmful ultraviolet (UVB) rays from the sun.

They analysed the skin of 100 volunteers who were exposed to six doses of UVB on two areas of their bodies – their backs and their buttocks.

After seven days, the volunteers' skin was analysed to find what colour remained after any redness had died down.

The scientists found that the buttocks were much more resistant to tanning, staying whiter than backs despite the same level of exposure.

The university said the study represents the first time that the depth of a tan, and not just skin redness, has been quantified.