Perfect tan a mythBottoms resist tanning
An even all-over tan may be impossible to achieve as some parts of the body are more resistant to tanning than others, a study has found.
Scientists at the University of Edinburgh say this may explain why some holidaymakers find it so hard to achieve an even tan all over their body.
Different types of skin cancer tend to be found in different parts of the body, but the reason for this remains a mystery, especially as all are caused by exposure to sunshine.
The researchers wanted to find out if this was linked to variations in the way different parts of the body developed a tan.
They analysed the skin of 100 volunteers, who were exposed to six dose of ultraviolet B rays (UVB) on two areas of their body - their back and their buttocks.
After seven days, the volunteers' skin was analysed to find what colour remained after any redness had died down.
The colour - which we call a suntan - comes from the skin’s production of melanin, a defence that blocks the skin absorbing too much harmful UVB radiation.
The researchers found that the buttocks were much more resistant to sunshine. And even when they go red, they tan less well than other parts of the body such as the back.
It was also found that people with no freckles tanned more easily than those with freckling.
Jonathan Rees, Professor of Dermatology at the University said: "One of the real puzzles about melanoma is why the numbers of tumours differ so much depending on body site.
"Our work shows that in one sense we are all made up of different units of skin, which respond differently to sunshine, and which all may afford different degrees of protection against the harmful effects of sunshine."
The findings are published in the journal Experimental Dermatology
This article was published on Tue 3 August 2010
Image © Nikolay Okhitin - Fotolia.com
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