Almost all basal and squamous cell cancers and the vast majority of melanomas can be linked to ultraviolet (UV) rays from the sun.
UV rays damage the DNA in skin cells, causing genetic mutations (defects). These mutations instruct the abnormal skin cells to multiply rapidly and develop malignant tumors.
Certain physical traits make this cascade of events more likely. People with light skin, for instance, produce less melanin, a pigment that can block out some (but not all) UV rays.
This can translate into racial or ethnic disparities in skin cancer risk. Yet while Caucasians are most vulnerable, people of color can also get skin cancer.
What’s more, they may detect it at a more advanced stage, when it is more difficult to treat.
Whether your odds of developing skin cancer are high or low, the smart move is to minimize any risks you can control and commit to regular dermatologist visits and skin self-exams.
Here’s a rundown on the most common — and a few uncommon — causes of skin cancer.
1. Too Much UV Exposure Is Hazardous
A lifetime in the sun and intermittent periods of intense UV exposure — the kind that causes sunburn — both raise skin cancer risk.
On average, a person’s risk of developing melanoma doubles if he or she has had more than five sunburns. (1)
Given the dangers, carefully and consistently taking UV-protective measures is especially critical if you:
- Have already had skin cancer
- Have a family history of skin cancer, particularly melanoma
- Have many moles or irregular or large moles (Most will never cause problems, but having many increases melanoma risk.)
- Tend to freckle or burn in the sun
- Have fair skin; blue, green, or gray eyes; or blond, red, or light brown hair
- Live at or regularly visit high altitudes, where UV rays are especially powerful
- Spend lots of time outside in the sun on weekends
- Spend a significant amount of time outdoors
- Have certain autoimmune diseases, like systemic lupus erythematosus (SLE, or lupus)
- Have had an organ transplant and take immunosuppressive medication
- Take medicine that suppresses the immune system regularly
- Take medicine that makes your skin more sensitive to sunlight
2. The Older You Are, the Greater Your Risk
The chance of developing skin cancer increases as you age, possibly because of the cumulative effect of many years of UV exposure.
But as skin cancer rates have climbed each year over the past several decades, the average age of onset has steadily decreased.
Dermatologists report treating more people in their twenties and thirties. The enormous popularity of indoor tanning beds, especially among young white women, may help explain why. (1)
Researchers estimate that the intense UV rays produced by these devices may be responsible for more than 419,000 cases of skin cancer in the United States each year: 245,000 basal cell carcinomas, 168,000 squamous cell carcinomas, and 6,200 melanomas.
To put that into context, consider that more people develop skin cancer because of indoor tanning than get lung cancer because of smoking. (1)
3. Men Are More Vulnerable Than Women
While women, especially young ones, have shown a troubling increase in skin cancer incidence rates over the past several decades, men are still more at risk.
Statistics show that men are more likely than women to have basal and squamous cell cancers of the skin.
Overall, men are also more likely to get melanoma than women. Before age 50, incidence is higher for women; after 50, it is higher for men.
The incidence of melanoma in men age 80 and older is three times higher than it is for women of the same age.
One reason may be that men know less about skin cancer than women, and so are less likely to take protective measures, such as using sunscreen.
A survey conducted by the American Academy of Dermatology in 2016 found that while 76 percent of the women interviewed agreed that “There is no such thing as a healthy tan,” only 56 percent of the men did.
Researchers also believe that men’s skin may be more susceptible to UV damage than women’s because it’s thicker, with less fat underneath, and contains more collagen and elastin.
Studies have found that men’s skin reacts more intensely to UV rays than women’s.
4. Exposure to Chemicals Can Increase Risk
Exposure to large amounts of arsenic, which is found in well water in some areas as well as in some pesticides, elevates the risk of developing basal and squamous cell cancers.
5. Some Medical Treatments Make It More Likely
People undergoing radiation treatment for cancer or ultraviolet light therapy for psoriasis are at higher risk for skin cancer.
Organ transplant patients taking drugs that suppress the immune system are also more susceptible to skin cancer.
6. Past Skin Cancer Might Mean Future Skin Cancer
Having basal cell or squamous cell carcinoma or melanoma increases the risk of developing these cancers again. Anyone who has had basal cell or squamous cell cancer is also at higher risk of developing melanoma. (4)
7. Other Types of Skin Problems Can Raise Your Risk
Researchers have discovered an association between skin cancer and severe scarring from burns, patches of skin over bone infections, and other types of damage related to certain inflammatory skin diseases.
8. Inherited Conditions May Leave Skin Susceptible
Xeroderma pigmentosum is an extremely uncommon inherited condition that leaves skin unable to adequately repair DNA damage from UV exposure.
People with basal cell nevus syndrome, a congenital condition that is usually inherited from a parent, will develop numerous basal cell cancers, sometimes beginning in childhood or adolescence.
9. Viruses Can Be a Skin Cancer Concern
HIV, the virus that causes AIDS, can lead to basal cell and squamous cell cancers by weakening the immune system.
Certain types of HPVs (human papilloma viruses), especially those affecting the genitals or anus or the skin around the fingernails, may lead to skin cancers in those areas.
10. Yet Another Reason Not to Smoke
Researchers have found a link between cigarette smoking and squamous cell cancer, particularly on the lips.