A recent study has said that it is impossible to get a consistent tan all over the body, as some parts are much more resistant to tanning than others.
The research said that getting a full uniform body tan has been deemed as a myth.
Researchers at the University of Edinburgh said that the results of the study explained why some holidaymakers find it so hard to achieve an even tan all over their body.
The findings show that the buttock is much more resistant to sunshine but surprisingly when it does go red it tans less well than other areas.
It was also found that people with no freckles tanned more easily than those without freckling.
The study represents the first time that the depth of a person's tan, and not just skin redness, has been quantified.
The study was carried out to understand why different types of skin cancer tend to be found in different parts of the body, given that they are all caused by exposure to sunshine.
The team's aim was to identify whether this is linked to variations in the way different parts of the body develop a tan. They analyzed the skin of 100 volunteers, who were exposed to six dose of UVB on two areas of their body - their back and their buttock.
After seven days, the volunteers' skin was analysed to find what colour remained after the redness had died down.
This colour recognized as a suntan comes from the skin's production of melanin, a defence that blocks the skin absorbing too much harmful UVB radiation.
"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," Professor of Dermatology at the University of Edinburgh, Jonathan Rees, who led the study said.
The study was published in the journal Experimental Dermatology.