As spring begins, fun in the sun—even artificial sun—beckons teenagers. Many, especially girls, flock to tanning salons to acquire a base tan for the beach and get that “healthy glow” for a strapless prom dress. But whatever the reason or the season, minors should not be allowed to lie in tanning beds. These devices are skin cancer factories, and people younger than 18 have the highest risk.

One fifth of girls in grades 9 through 12 have bathed in ultraviolet (UV) rays from a tanning device in the past year, and one out of 10 girls reported popping into a tanning bed at least 10 times during that period, according to the Youth Risk Behavior Survey of 2013. (Only 5 percent of teen boys used beds at all.) The 14,000 tanning salons in the U.S. make that access easy. The quest for a tan contributes to frequent visits, but the behavior is also addictive. Basking under the bulbs releases opioid endorphins that increase relaxation and boost positive feelings that make patrons seek out the exposure again.

Their skin cells, however, are not happy. UV rays damage cellular DNA, which increases the chances those cells will become malignant. Radiation from indoor tanning devices is often more intense than the sun's natural rays. In a typical indoor tanning session, a person faces UV radiation at least as strong as midday sun in southern Europe. Concern over this intensity led the World Health Organization in 2009 to reclassify tanning devices as a high-level carcinogen—their most dangerous designation, which also includes cigarettes and plutonium. The number of skin cancer cases linked to tanning beds every year is two times the number of lung cancer cases associated with smoking.

The evidence of the danger continues to mount. Last year a systematic review and meta-analysis of 88 studies concluded that the beds lead to over 10,000 new cases of melanoma—the deadliest form of skin cancer—every year in the U.S., Australia and Europe and as many as 450,000 cases of other skin cancers.

The tanning habit is dangerous for anyone but especially risky for young users because the earlier UV damage begins, the more time it has to add up and get worse. People who begin tanning before the age of 35 have a melanoma risk that is at least 60 percent greater than those who start after that age. Melanoma is the second most common cancer among women in their 20s, and its incidence in those young women continues to rise, even as the rates of most other cancers have stabilized.

Because the hazards are so clear, Brazil outlawed artificial tanning for all its citizens—regardless of age—in 2011. Most of Australia's states and territories did the same as of this January. Nor can minors step foot in tanning salons in 11 European countries, including the U.K., France, Germany and Spain.

In the U.S., however, safety measures have been scattershot. Last year the Food and Drug Administration ordered that all tanning devices must carry a “black box” label warning that states indoor tanning is known to cause cancer and that minors should avoid it. Various states require parental consent, time limits and mandatory eye protection. Research shows, however, that these small-scale efforts are ineffective. Currently 10 states have absolute bans on the books for minors.

The U.S. needs a national ban so that all minors are protected immediately. Opponents, such as the Indoor Tanning Association, argue that such laws take away parenting rights and represent a slippery slope of growing government interference. But the health of our society's youngest members is paramount. The WHO, the U.S. Department of Health and Human Services, and leading medical societies support a ban for minors. We don't allow anyone younger than 18 to buy cigarettes. It is time to stop them from frying under bulbs.