The World Health Organization (WHO) has issued a report warning people younger than 18 to stay away from tanning beds because they can raise the risk of skin cancer.

The global health agency issued the advisory because many teens, especially girls, like to use the beds to get a tan before summer starts.

"There has been mounting concern over the past several years that people, and in particular teenagers, are using sunbeds excessively to acquire tans which are seen as socially desirable," according to Kerstin Leitner, PhD, the WHO assistant director-general for environmental health. "However, the consequence of this sunbed usage has been a precipitous rise in the number of skin cancer cases."

Skin cancer is the most common type of cancer in the United States. According to American Cancer Society estimates, more than 1 million cases of basal cell or squamous cell skin cancers occur every year. These types of skin cancer are highly curable, but about 1,000 -2,000 Americans die from them each year.

Melanoma, however, is more dangerous. This type of skin cancer strikes more than 59,000 people in the US each year and kills more than 7,000. Melanoma is becoming more common in the US and other countries around the world, according to WHO statistics, and the popularity of tanning and tanning beds is part of the reason.

Like tanning in the sun, tanning in a bed exposes the skin to damaging ultraviolet (UV) radiation. This exposure raises the risk of developing skin cancer, even if a person doesn't get burned.

There is no evidence that tanning in a bed is any safer than tanning in the sun -- in fact, some tanning beds release much stronger UV light than the sun does. And at least one study has shown that women who tan in beds are more likely to develop melanoma than those who don't.

UV exposure in childhood is thought to be especially dangerous.

The WHO warned that skin cancer isn't the only possible consequence of too much tanning. Excessive UV exposure can also cause eye damage (including cataracts) and premature skin aging, and may even harm the immune system.

Leitner said the agency has a clear message: "Avoid excess exposure to UV and when you have to be in the sun, protect your skin."