Learn how to protect your skin from the sun with tips from Tufts Medicine dermatologist Joshua Mervis, MD, FAAD.
What are UV rays, and how do they affect my skin?
UV (ultraviolet) rays are invisible rays from the sun that can damage skin cells. There are 2 main types:
- UVA rays: Cause skin aging and wrinkles
- UVB rays: Cause sunburn and play a key role in skin cancer development
Both can harm your skin even on cloudy days, leading to sunburn, premature aging and increased risk of skin cancer—including melanoma.
How does SPF work?
The SPF (Sunscreen Protection Factor) is a ratio of how long you can stay in the sun without getting sunburned while wearing sunscreen compared to unprotected skin. For example, if your skin usually burns after 10 minutes in the sun, an SPF 30 sunscreen could help protect you for up to 300 minutes.
What kind of sunscreen should I use?
The best sunscreen is the one you’ll actually use. But I recommend skipping spray or aerosol sunscreens—they're easy to apply unevenly or miss spots. For the best protection, choose a sunscreen that is:
- SPF 30 or higher
- Water resistant
- Broad spectrum (protection against both UVA and UVB rays)
How often should I apply sunscreen?
You should wear sunscreen every day—even when it’s cloudy or cold. Up to 80% of UV rays can pass through clouds, and snow can reflect the sun’s rays, increasing your exposure. Sunscreen is important year-round.
When you're outside, reapply every 2 hours—and right after swimming or sweating.
Use about 1 ounce of sunscreen (a full shot glass) to cover your whole body. Don’t forget easy-to-miss spots like your ears, neck, the back of your hands, tops of your feet and your scalp (or wear a hat). Your lips need protection too—use a lip balm with SPF 30 or higher.
What are some of the common sun protection mistakes you see?
One thing I see often in my practice is that men are less likely than women to use sunscreen every day. But sun protection is important for everyone—especially during intense sun exposure, like at the beach, doing yardwork or playing tennis or golf.
I always remind people to protect their scalp by wearing a hat, especially if they’re bald or have thinning hair.
Do I have to wear sunscreen if I have dark skin?
Everyone should wear sunscreen, regardless of skin tone. While darker skin offers some natural protection, people of all skin tones can develop skin cancer. Melanin doesn’t block all of the sun's harmful rays, so sunscreen adds an important layer of protection against skin cancer, hyperpigmentation, and premature aging.
Are tanning beds safer than the sun?
No, even one use of a tanning bed increases your risk of skin cancer development. If you want a sun-kissed look, try a self-tanner or spray tan—these give you color without the harmful UV exposure.
What are the signs of sun damage?
- Wrinkles or fine lines
- Dark spots or discoloration
- Rough or leathery skin
- New or changing moles or sunspots (see a dermatologist for evaluation)
When should I see a dermatologist?
Schedule a skin check if you:
- Notice a new or changing mole, especially one that looks different from your other moles
- Develop an itchy, bleeding or painful skin growth
- Have a personal or family history of skin cancer
The bottom line?
Wear sunscreen and protective clothing every day, talk to your doctor about your risk factors and schedule an annual skin check.
