Teenagers girls are flouting the law and putting their health at risk by using sunbeds, research suggests.
Girls aged 15 to 18 told scientists they regularly used sunbeds because a tan made them look healthier and feel more confident.
They knew about the potential dangers, including premature ageing and deadly skin cancer, but were willing to accept or ignore them.
In 2011 it became illegal in England and Wales for young people under the age of 18 to use sunbeds.
This was after figures released the previous year showed that 250,000 children aged 11 to 17 in England were regularly visiting tanning parlours.
But the law is falling short because it is so difficult to police, say experts. Salons are not always supervised by trained staff who can stop young teenagers using their equipment.
The new research emerged from focus group meetings involving 69 teenagers in six cities around the UK.
Girls who regularly used sunbeds were asked questions that explored their motivations and attitudes, and knowledge of health risks.
Health consultant Dr Jeffrey Lake, who led the study published in the Journal of Public Health, said: "The research shows us that the desire for tanned skin in young people is blinding them to the potential long-term health risks associated with regularly using sunbeds.
"We're finding that their worries are cosmetic when they should really be thinking about the unseen damage they're inflicting on themselves."
Co-author Catherine Thomson, head of statistical information at the charity Cancer Research UK, said: "It's worrying to see that, in some areas of the UK, half of all 15-17 year-old girls are using sunbeds on a regular basis.
"Introducing the legislation banning sunbed use by under 18s was vital to protect younger people from the harmful effects of UV. But proper supervision in salons is essential to combat the determination of teenagers to get round laws that are there for their own protection."
The findings are published just over a week before Cancer Research UK launches its R UV UGLY? campaign for the second time in England.
As part of the campaign, people will be offered free cosmetic skin scans at skin clinics across the country.
The technology will be used to highlight hidden cosmetic damage beneath the skin's surface, such as pigmentation and premature wrinkles, caused by overexposure to UV both from sunbeds and the sun.
Yinka Ebo, senior health information officer at Cancer Research UK, said: "This study shows that we need to persuade teenagers that damaging their health really isn't justified by the promise of a tan.
"Sunbeds aren't harmless and research has showed that using them for the first time before the age of 35 increases the risk of developing melanoma, the most serious form of skin cancer, by 59%."
The Sunbed Association, which represents tanning salon operators and sunbed manufacturers, hit back at the research, insisting that it lacked credibility.
Chairman Gary Lipman said: "We know for an absolute fact that under-age use of sunbeds has never been a widespread problem.
"It is even less of one now that it is illegal for under-18s to use a sunbed, a move which we totally supported.
"This very small sample study questioned 69 15-to-18-year-olds. Under-18s would not be allowed to use a sunbed in our members' salons.
"We acknowledge that pre-pubescent skin should not be exposed to UV rays either on a sunbed or in sunlight, and neither should adults with sensitive skin. In these instances, we would encourage use of spray tans or sunless tanning creams to get a tan.
"All our members have properly trained staff in their salons and this includes being able to advise everyone seeking a tan about the most responsible way to achieve it. For those under-18 and for those over 18 with other contra-indications, this would be to refuse use of the sunbed and offer or advise on UV-free alternatives.
"Quite frankly, this alleged qualitative investigation by Cancer Research UK is so lightweight it's embarrassing.
"With a sample of around five people per group aged 15-18 and a total of 69 nationally, it is both misleading and completely disingenuous for Catherine Thomson, head of statistical information at Cancer Research UK and co-author of the study, to claim that in some areas of the UK, half of all 15-to-17-year-old girls are using sunbeds on a regular basis.
"This outrageous claim would also have had to allow for the 18-year-olds in the sample of 69 to be omitted from the findings - so in reality, the sample could actually be much lower than 69 people.
"She, better than most, should appreciate that sample size is crucial. With too small a sample you simply cannot have sufficient data to reach any meaningful conclusions."
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