According to the April issue of the Mayo Clinic Health Letter, half of all new cancers in the United States are skin cancers. The letter also states that one in five Americans will develop the cancer, and the chances of getting it doubles if an individual has had five or more sunburns.

Mayo Clinic researchers documented the increase by tracking skin cancer incidence in adults under age 40 in southern Minnesota. Between 1976 and 2003, the incidence of basal-cell skin cancers—a nonmelanoma skin cancer—roughly tripled in women, to more than 30 per 100,000. The rate increased slightly among men, from about 23 to nearly 27 per 100,000.

Typically, 90% of nonmelanoma cancers develop on sun-exposed skin, such as on the head and neck. But in this study, only 60% of the cancers were found on sun-exposed skin, leading to the suspicion that visits to the tanning booth might account for many of the other 40%.

To prevent skin cancer, physicians should recommend that their patients: use generous amounts—at least 1 ounce—of sunscreen to protect their skin from the sun’s rays; apply sunscreen about 30 minutes before they go out and reapply every 2 hours and; wear protective clothing, a broad-brimmed hat, and sunglasses. Physicians should also remind patients that tanning salons are dangerous because occasional yet intense UVA exposure poses a greater  risk of melanoma skin cancer than does spending long hours in the sun.