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Last updated on April 23, 2014 at 21:24 EDT

Scientists: Body Parts Tan Differently

August 8, 2010

According to researchers at Edinburgh University, people may be disappointed when trying to get tan by soaking up sunrays this summer.

The researchers said that different parts of the body go brown at different speeds, so achieving that idealized image of beauty is not going to happen.

The findings explain why certain people find it difficult to get an even, consistent tan.  The main problem is people’s bottoms, which take a lot longer to go brown than other parts of their anatomy.

Ninety-eight volunteers were given six doses of ultraviolet radiation on their backs and their bottoms from a tanning light in order to determine the effect was the same in both places.  Once the researchers examined the participants a week later they found that their backs had turned significantly browner than their buttocks.

“The research shows that instead of thinking that you have got one skin, or one skin type, in fact each of us has lots of different skin regions, each of which responds differently to UV light and so take longer than others to go red and then tan,” said Jonathan Rees, a professor of dermatology, who led the study.

“If you shine sunshine on different parts of your body, the difference in how red they go varies by a factor of five for redness and two for tanning, depending on the body site.”

The bottom is not the only obstacle though.  Rees has confirmed previous research that showed that sun worshippers already knew that the upper back is much more likely to tan than the legs.

“What is burning for one body site is not for another. And the degree of UV protection that develops following ultraviolet radiation exposure may vary site by site,” Rees added.

The study also found that those who had no freckles on their skin tanned easier than those with freckles.

Rees and his team looked into why different types of skin cancer occur in different parts of the body.  Usually they develop on ears, faces and the backs of hands and on the top of the head, rather than on the limbs.  Rees said that women get Melanoma on their calves but men get it on their shoulders.

He said the findings show that most advice about how long it is safe to spend in the sun is worthless because different body parts are more sensitive to the sun’s damaging effects than others.