Regular sunscreen use, protective clothing, and avoiding peak UV hours are the most effective ways to prevent squamous cell carcinoma (SCC), the second most common skin cancer. Daily use of SPF 15 or higher sunscreen reduces SCC risk by about 40%. But sun protection is just one layer of a broader prevention strategy that includes self-exams, treating precancerous spots, and addressing less obvious risk factors like smoking and arsenic exposure.
Why UV Exposure Drives SCC
Ultraviolet radiation causes SCC by physically damaging the DNA inside skin cells. When UV rays hit your skin, they create defects in the genetic code of keratinocytes, the cells that make up your skin’s outer layer. One of the most important targets is a gene called TP53, which normally acts as your body’s tumor suppressor, catching and correcting errors before they spiral into cancer. UV radiation is particularly good at disabling this gene because the DNA repair process at those specific sites is slow.
The damage is cumulative. Each sunburn and each hour of unprotected exposure adds mutations that your skin cells carry permanently. This is why SCC tends to appear on areas with the most lifetime sun exposure: the face, ears, scalp, backs of the hands, and forearms. The lag between UV damage and cancer formation can be decades, which means prevention at any age still matters.
Clothing Outperforms Sunscreen
Protective clothing is the single most reliable barrier against UV radiation. In head-to-head testing, common fabrics blocked 96% to 98% of UVA rays, the type that penetrates deep into skin. Even the best-performing sunscreen (SPF 50 applied at full thickness) topped out at about 82% UVA blocking. For UVB rays, the gap was similar: fabrics tested at SPF values between 60 and 80, well above what most sunscreens deliver in real-world use.
The practical advantage of clothing is that it works consistently. Sunscreen’s effectiveness drops when you apply too little, miss spots, sweat it off, or forget to reapply. A long-sleeved shirt, wide-brimmed hat, and sunglasses don’t have those failure points. Look for garments labeled UPF 50, which block about 98% of UV radiation. Darker colors and tighter weaves perform better than light, loosely woven fabrics.
Sunscreen still matters for exposed skin, particularly your face, ears, neck, and hands. Choose broad-spectrum SPF 30 or higher and reapply every two hours when outdoors, or immediately after swimming or sweating. The 40% reduction in SCC risk from daily sunscreen use only holds when it’s applied consistently, not just on beach days.
Spot and Treat Precancerous Lesions
Actinic keratoses are rough, scaly patches caused by years of sun damage. They’re the most common precursor to SCC. The risk of any single lesion progressing to invasive cancer is low, estimated at less than 0.1% per year. But that number climbs quickly when you have multiple lesions or widespread signs of sun damage across a region of skin, a pattern dermatologists call field cancerization.
Treating actinic keratoses early removes the cells most likely to turn malignant. Options include freezing individual spots with liquid nitrogen, applying prescription creams that trigger the immune system to clear abnormal cells, or photodynamic therapy that uses light-activated medication to destroy precancerous tissue. Your dermatologist will recommend an approach based on how many lesions you have and where they are. If you’ve had actinic keratoses before, plan on regular skin checks, since new ones are likely to develop in the same sun-exposed areas.
Know What SCC Looks Like
Monthly self-exams help you catch changes early, when treatment is simplest. SCC can show up as a firm bump on the skin that may be pink, red, brown, or skin-colored. It can also appear as a flat sore with a scaly crust that doesn’t fully heal, a new raised area on an old scar, or a rough, scaly patch on the lip that eventually opens. Inside the mouth, on the genitals, or around the anus, SCC can look like a raised patch or wartlike sore.
Pay special attention to areas that get the most sun: your face, ears, neck, scalp (especially if you have thinning hair), forearms, and the backs of your hands. Any sore that bleeds, crusts over, and then reopens, or any new growth that persists for more than a few weeks, is worth showing to a dermatologist.
Quit Smoking
Smoking increases the risk of squamous cell carcinoma of the head, neck, and lips. The good news is that the risk starts dropping within the first five years of quitting. After 10 years, former smokers cut their risk roughly in half compared to current smokers. After 20 years of not smoking, risk approaches that of someone who never smoked at all, dropping to about one-fifth the risk of a current smoker.
Reduce Arsenic Exposure
Arsenic is classified as a Group 1 human carcinogen, and exposure is linked to a roughly 64% increase in SCC risk. The World Health Organization recommends drinking water contain no more than 10 micrograms per liter of arsenic, though many developing countries allow up to 50. In the United States, arsenic in rice has been associated with a 1.5 times higher likelihood of developing SCC compared to people who don’t eat rice.
If you rely on well water, testing for arsenic is inexpensive and available through local health departments. For rice, rinsing it thoroughly and cooking it in excess water (then draining) reduces arsenic content. Varying your grains so rice isn’t a daily staple also helps lower cumulative exposure.
Nicotinamide for High-Risk Individuals
Nicotinamide, a form of vitamin B3, has shown promise for people who’ve already had skin cancers. In a randomized trial published in the New England Journal of Medicine, taking 500 mg of nicotinamide twice daily for 12 months reduced the rate of new squamous cell carcinomas by 30% compared to placebo. It’s inexpensive, available over the counter, and was well tolerated in the study. The benefit appears to last only while you’re taking it, so it’s a maintenance strategy rather than a one-time fix. This supplement is most relevant if you have a history of multiple skin cancers or widespread sun damage.
Extra Vigilance After Organ Transplant
Organ transplant recipients face dramatically higher SCC risk because the medications that prevent organ rejection also suppress the immune system’s ability to detect and destroy abnormal skin cells. Prevention for transplant recipients follows a tiered approach: routine skin surveillance and strict sun protection for everyone, with more aggressive interventions added as the level of skin damage increases.
For transplant recipients with early signs of widespread sun damage, dermatologists typically treat precancerous areas with prescription creams or photodynamic therapy. If invasive SCCs begin appearing, oral medications that slow skin cancer growth may be started. For those developing multiple or aggressive cancers, the transplant team may consider adjusting the type or dose of immune-suppressing medication. If you’ve had an organ transplant, regular dermatology visits (often every 6 to 12 months, or more frequently if you’ve had skin cancers) are essential.