Using sunbeds can significantly increase the risk of a potentially serious skin cancer that is more common than melanoma, a study suggests.
Researchers said warnings about sunbeds often focus on melanoma, the least common type of skin cancer, which is linked to sunburn.
However, scientists at the University of Dundee and Leiden University Medical Centre in the Netherlands have issued a warning about squamous cell carcinoma (SCC) - the second most common type of skin cancer.
They said it is caused by longer-term, cumulative ultraviolet exposure such as through repeated tanning, rather than isolated incidents of burning.
The team looked at UV intensity levels recorded in a previous study, the average length of sunbed sessions, the number of sessions each year, as well as a person's cumulative UV exposure from the sun, and then applied an equation that links UV exposure and SCC incidence, to predict risk to people who use sunbeds.
The researchers found that by the age of 55, people who regularly used a sunbed were 90 per cent more likely to develop SCC than those who did not.
Sunbed use was defined as having a 12-minute session about every eight days or a six minute session every four days, over a 15-year period from age 20 to 35, using a sunbed with a median UV dose.
For high dose sunbeds the risk is increased by 180 per cent and even the sunbeds giving the lowest dose found in the 2013 study were linked to a 40 increased risk.
"There is considerable variation in the output of artificial tanning units which people should be aware of," Professor Harry Moseley of the University of Dundee, one of the study's authors, said.
"The results of our study indicate that the additional UV dose from sunbed use compared to normal day-to-day sun exposure potentially adds a significantly increased risk for development of SCC."
Nina Goad of the British Association of Dermatologists said: "While other types of skin cancer, such as melanoma, are linked to sunburn, SCC is caused by more chronic, long-term, cumulative sun exposure.
"One defence of the sunbed industry is that sunbeds do not increase your risk of skin cancer if you do not burn. However this study weakens this argument. It is something that people should be warned about, so they are fully informed of the risks when making choices about sunbed use."
The team are presenting their findings this week at the World Congress on Cancers of the Skin in Edinburgh.
