Daily sunscreen use lowers the risk of melanoma and squamous cell carcinoma, and it remains the most effective anti-aging step available, since the vast majority of visible skin aging comes from UV exposure, sunscreen only works when it’s applied fully. Missed areas leave skin vulnerable, even with regular use. Research published in the journal PLOS One found that people leave about 20% of their exposed skin unprotected on average.

Below are five areas dermatologists say get skipped most often, along with tips for fixing the problem.

1. Scalp and hairline

The scalp, including the hairline and part, is one of the most commonly missed zones. Skin cancers frequently appear high on the forehead near the hairline, largely because sunscreen doesn’t get rubbed in thoroughly there. A spray formula can make the area easier to cover. The stakes are high: scalp melanoma is six times more common in men than in women and tends to behave more aggressively than melanoma elsewhere on the body, according to a 2021 study review. It also gets diagnosed later than average, since hair can hide early warning signs. Wearing a tight weave hat and scheduling annual dermatologist skin checks can help close the gap.

2. Lips

SPF lip balm is another frequent miss. Doctors report seeing a notable number of precancerous and cancerous lesions on the lips, a direct result of skipping this step.

3. Ears, eyelids and nose

These three areas receive high UV exposure but rarely get consistent sunscreen coverage. Mohs surgeons, who remove skin cancer by shaving away thin layers of tissue, say they disproportionately treat cancers on the ears and nose.

4. Upper middle back

This stretch of skin sits just beyond where most people’s arms can comfortably reach, making it nearly impossible to cover alone. Enlisting a partner for help, and having them cover the back of the neck and legs while they’re at it, closes a major blind spot.

5. The right way to apply it

Choosing between mineral sunscreen, such as zinc oxide, and chemical sunscreen matters less than using either one consistently and in the right amount. Most people apply only 25% to 50% of the sunscreen needed to reach the SPF listed on the label. Skin cancer rarely results from a single bad sunburn. It typically stems from years of under-protection.

5 rules for better coverage

1. Use enough product. A full shot glass covers the body, and a nickel sized amount covers the face. For an easy face measurement, apply a line of sunscreen along the index and middle fingers from tip to palm; that amount is generally enough for full facial coverage.
2. Reapply every two hours, or more often when sweating or swimming. Chemical sunscreen ingredients break down over time, and mineral ingredients can clump, both of which reduce effectiveness without any visible warning sign.
3. When using spray sunscreen, hold the bottle about an inch from skin and spray until it visibly glistens before rubbing it in. If it isn’t visible, it isn’t providing protection.
4. With stick sunscreen, swipe back and forth across the skin four times to deposit enough product, then rub it in by hand.
5. Pair sunscreen with additional protection, including hats, sunglasses and shade during peak UV hours, rather than relying on SPF alone.

Choose broad spectrum sunscreen rated SPF 30 or higher, and apply it as one part of a complete sun safety routine rather than the only defense.