Fully half of all cancer cases are skin cancer, making it the most common type of cancer in the U.S. In fact, one in five Americans will be diagnosed with skin cancer at some point in life. You probably know that your risk of developing skin cancer is greater if you're fair skinned and burn easily. Who else should worry?
Check the following 13 clues to who will get skin cancer. If you're in one of these groups, you'll want to be vigilant about using sunscreen, making regular skin checks, and avoiding the sun's harshest midday rays.
Clue #1: You often wear flip-flops.
Before flips-flop sandals came along, most leisure shoes were sneakers or sandal styles, like huaraches, which largely covered the feet. In barely-there flip-flops, your toes and the tops of your feet are in danger of damaging burns unless you add sunscreen or socks. Flimsy footwear can also lead to irritations, cracking, bleeding, and open sores -- which are the most common sites for foot skin cancers to develop. Unfortunately, feet are often overlooked during skin checks, according to the American Podiatric Medicine Association.
Scary stat: Half of those diagnosed with melanoma of the foot die within five years because the cancer has already spread through the body, says the American College of Foot and Ankle Surgeons.
Smart step: Cover your feet whenever you can with sunscreen or footwear -- or a blanket. "On the beach, people tend to fall asleep on their stomach, leaving the soles of the feet exposed. You can then get severe burns there," says dermatologist Diane C. Madfes, assistant clinical professor at Mt. Sinai School of Medicine in New York City and a spokesperson for the American Academy of Dermatology. "It's easy to just throw a towel over your feet first."
Clue #2: You wear baseball caps.
Many of us grab a ball cap to shield our eyes and face from the sun -- too bad these hats leave the tips of the ears exposed to damaging UV rays. And the ears happen to be an area of skin that most people don't remember to slather with sunscreen.
Scary stats: Ears are also the third most common site of basal cell carcinoma (the most common form of skin cancer). The ear is where doctors often find squamous cell carcinoma (an easily-treated form, usually found on sun-exposed skin). In a 2007 study, most victims of ear skin cancer were men; their shorter hair is also thought to be a factor.
Smart step: Along with remembering to dab sunscreen on your ear tips, pay extra attention to your cheek tops. Hat brims and sunglasses often provide coverage that stops right there, Madfes says. "We see a lot of spots from sun damage at the rim just under the glasses."
Clue #3: You're a man.
Scientists aren't sure if habits, genes, or hormones -- or a combination of these and other factors -- are to blame. (Women, for example, may get more protection from their makeup, whether or not it contains zinc and SPF, as well as from their longer hair, Madfes says.) Whatever the reason, men have three times more squamous cell cancers and twice as many basal cell cancers as women, and after age 40, more cases of melanoma, the deadliest form. In fact, white men over age 50 have the highest incidence of melanoma.
Scary stats: Melanoma is one of only three cancer types with mortality rates still on the rise in men (along with liver cancer and esophageal cancer). Men get skin cancer more often than colon, prostate, and lung cancer.
Smart step: If, like many men, you dislike applying lotion to your face, consider one of the newer powder sunblocks. "Quick swipes of the face and ears with a powder are easier for some guys," Madfes says.
More surprising clues to skin cancer risk
Clue #4: You have dark skin.
It's true that skin with more pigment has a greater natural shield against damaging UV rays, so it's less likely to turn cancerous. But this lulls many African-Americans, Hispanics, Asian Indians, and others with deep skin tones into a false sense of security about the need for sun protection.
Scary stat: : It's more common for melanoma diagnoses to come at later stages among blacks and Asians than among white patients. Late-stage detection makes melanoma more difficult to treat.
Smart step: Keep your eyes on the most vulnerable areas of skin for those who are dark: the palms of the hands, the soles of the feet, between the toes, and around or under the toenails. (Musician Bob Marley died at 36 from melanoma on the foot.)
Clue #5: You live in the South or in the mountains.
Where you live (or vacation) can affect your skin health. Rates of skin cancer run higher in places that are exposed to more sunlight. More Texans and Floridians get skin cancer than Minnesotans or Alaskans, for example. Altitude is also a risk factor, because UV radiation from the sun increases about 4 to 5 percent for every 1,000 feet above sea level. UV damage is cumulative: The more time you lived or vacationed in such places, the higher your risk.
Scary stats: A 1999 study found that UV-B levels in Vail, Colorado, were the same as in Orlando, Florida -- and 60 percent higher than in New York City.
Smart step: Remember that you burn faster when skiing or hiking in the mountains. Look for hats with flaps on the back that cover the neck; the back and sides of the neck get more incidental exposure and are a common site for UV damage, Madfes says.
Clue #6: You're a runner, cyclist, or swimmer.
Athletes in any sport who spend hours outside sweating, while wearing shorts or swimsuits with exposed limbs, raise their sun-damage risk. Intensive athletes tend to invest so much time at these sports that even those who routinely use sunscreen are unlikely to refresh it after it sweats off.
Scary stat: Marathoners had more risk factors for skin cancers than nonrunners in a 2006 study by dermatologists at the Medical University of Graz, Austria. The more miles the men and women subjects (ages 19 to 71) ran, the more atypical moles and skin lesions they had.
Smart step: Take advantage of the cutting-edge sportswear that's made to provide UV protection while wicking away sweat so that comfort and performance don't suffer.
Clue #7: You have a lot of moles.
Moles -- small, relatively round spots that are red, pink, or brown -- are a normal skin occurrence known as nevi. Caucasians have an average of 30 moles, but some people (of any race) have a genetic tendency to more. It's the dysplastic nevi -- moles that are asymmetrical, with raggedy borders, changing size, or a multicolored appearance -- that are more likely than ordinary moles to develop into deadly melanoma. Even so, people over age 20 who have more than 100 moles of any kind (or more than 50 moles, for those under 20) should be especially careful.
Scary stat: Although most nevi and dysplastic nevi don't become melanomas, the chance of a melanoma is about ten times higher for someone who has more than five dysplastic nevi than for someone who has none. The more moles you have overall, the more likely that one or more may be dysplastic.
Smart step: Dermatologists use a high number of moles as a marker for possible skin cancers, but everyone benefits from skin checks at least annually. ("Check your birthday suit on your birthday," advises the American Academy of Dermatology.) Use a mirror to help you do a thorough self-exam. Report moles that grow, change shape, bleed, or itch. A professional full-body skin screening, typically done by dermatologists, is a visual exam that takes less than ten minutes.
Clue #8: You have light-colored eyes.
Are your eyes baby blues? Scarlett O'Hara's pale green? Mysterious gray? Better buy extra sunscreen. Blue, green, or gray eyes are considered risk factors for skin cancer, partly because they so often occur with fair skin, lots of freckles, and blonde or red hair -- other high-risk traits. Hair and eye color are determined by the same genes that determine the amount of melanin in skin -- the light-absorbing pigment that protects against harmful UV rays.
Scary stat: One in 35 Caucasian men and one in 54 Caucasian women will develop melanoma in his or her lifetime.
Smart step: The amount of sunscreen needed to adequately cover your body fills a shot glass, according to the American Academy of Dermatology. Most people apply only one-fourth to one half the necessary amount. No matter what your skin or eye color, don't forget your lips -- skin cancer can form there, too. So apply a lip product with 30 SPF or higher.
More surprising clues to skin cancer risk
Clue #9: You got lots of sunburns as a kid or teen.
A history of sunburn is one the most common causes of skin cancer, according to the American Cancer Society. Your risk doubles if you've had more than five sunburns at any point in your life. And can you remember any tortuous burns that blistered? Just one blistering burn can double the risk of developing melanoma later in life, according to the Melanoma Research Foundation.
Scary stat: Between fifth grade and eighth grade, there's a 50-percent drop in the number of kids who use sunscreen as junior sun-worshippers actively seek a tan, according to a 2012 study in the journal Pediatrics.
Smart step: Don't take a fatalistic attitude to past burns and figure you're doomed. "Sure, damage was done, but cells regenerate every day," Madfes says. "You don't need to increase your risk by continuing to burn as an adult." And if there's a preteen or teen in your life, keep nagging about the sunscreen -- and set a good example yourself.
Clue #10: You have a "healthy" tan.
We associate sun-kissed skin with health -- but technically, that tan is evidence of UV damage. "Sorry, but there's no such thing as a 'base tan' that protects you from further damage," says Madfes.
Scary stats: Overall skin cancer rates are up 300 percent since 1994, according to the Skin Cancer Foundation. Rates of melanoma -- the deadliest form of skin cancer -- have been rising for the past three decades, according to the American Cancer Society, with the fastest rise in women ages 15 to 39.
Smart step: Content yourself with the natural color you receive from incidental sun exposure, which you get even when wearing sunscreen, Madfes says. (You'll visibly age better, too.) For more tan, stick to UV-free artificial topical tanners or bronzers -- but remember they don't contain sun protection, so you'll also need to apply sunscreen.
Clue #11: You smoke.
The lungs aren't the only body part damaged by nicotine. Women with squamous cell carcinoma were more likely to have smoked, found a 2011 study at Tampa's Moffitt Cancer Center at the University of South Florida. Researchers aren't sure why women smokers were more affected, but they think that estrogen affects how nicotine is metabolized. Smoking also lowers immunity and introduces more damaging free radicals to your system, Madfes says.
Scary stats: For both sexes, the longer you smoke, the more likely you'll develop nonmelanoma skin cancer. After 20 years of puffing, your odds of skin cancer double, compared to nonsmokers.
Smart steps: Quitting, of course, lowers your risk of all kinds of cancers. And that also reduces the secondhand smoke that your loved ones inhale, which is linked to a variety of cancers.
Clue #12: You've used a tanning bed -- even once.
Although the risk is highest in frequent users of sun lamps and tanning machines, even occasional users have three times the risk of skin cancer as someone who has never used artificial UV light to tan. "Even once causes ongoing damage," Madfes says.
Scary stats: Glow-seekers who use tanning beds are 69 percent more likely to develop basal skin cancer before age 40, according to a December 2011 report in the Journal of the American Academy of Dermatology. Use a tanning bed once a month if you're under age 35, and your risk of getting melanoma skyrockets to 75 percent.
Smart steps: There's a movement around the country to restrict use of tanning beds by minors under 18, with or without parental permission. A law effective January 1, 2012, in California, for example, prohibits minors under 18 from using a tanning facility. (For a state-by-state list of pending bills, see AimatMelanoma.org.)
Clue #13: You're in treatment for an autoimmune disease or organ transplant.
They may not seem an obvious connection, but treatments for autoimmune diseases or organ transplantation raise skin-damage risks. In the case of rheumatoid arthritis, TNF inhibitors -- a type of medication that includes Cimzia, Enbrel, Humira, Remicade, and Simponi -- increase the risk of nonmelanoma skin cancers by 45 percent, according to a 2011 study. Similarly, sufferers of inflammatory bowel disease (including Crohn's disease) who take the immunosuppressant drugs called thiopurines are more vulnerable to basal cell carcinoma, according to a pair of studies in the November 2011 issue of Gastroenterology.
Scary stat: A large study in 2005 found that, due to immunosuppressants, those who receive kidney transplants are four times more likely than the general population to develop melanoma.
Smart steps: Add sunscreen to your routine year-round, in sun or shade. Wondering if your old bottle of sunscreen is still good? Technically you should be using it every day, so there's never a dated bottle hanging around. Check for an expiration date and abide by it, dermatologists say. If you don't see one, the contents are good for three years from manufacture, according to FDA requirements.