Does sunscreen cause cancer? How do we get vitamin D if we use sunscreen? Addressing sunscreen myths

As a dermatologist, I hear a lot of misconceptions surrounding sun exposure and sunscreen. There’s usually a kernel of truth to those misunderstandings, but that bit of truth can get exaggerated or used to support claims that are false and can even be harmful.

Myth: Sunscreen is an unnecessary modern invention – our ancestors survived without it

The sun is a natural part of our environment. But even things that are 100% natural can be harmful to us.

Most of human history took place before the invention of sunscreen. Over time, human skin evolved to match the environments of our ancestors. For example, if your ancestors were from Ireland, you might have naturally fair skin. If you live in a sunnier area like Florida, your skin hasn’t evolved for the intensity of year-round sunshine in the same way as someone’s whose ancestors lived closer to the equator.

Myth: Sunscreen causes cancer

Sunscreen use has increased over time. Rates of diagnosed melanoma (the most dangerous type of skin cancer) have increased over time.

How do we know sunscreen didn’t cause the melanoma? And why hasn’t increased sunscreen use led to fewer melanoma diagnoses?

• Melanoma typically develops decades after the sun exposure that caused it. Melanoma that’s diagnosed in a 65-year-old today may reflect UV damage that happened in the 1980s or '90s, when sunscreen use was less common.
• We’ve gotten much better at spotting melanoma, so we’re finding cancers today that might have gone undiagnosed in the past.

There is some evidence that people who say they use sunscreen regularly are some of the same people who have higher rates of skin cancer. However…

• People who most need sunscreen already have the highest risk of skin cancer. Sunscreen users are more likely to be fair-skinned, burn easily and spend lots of time at the beach or pool.
• Studies that account for these variables show that sunscreen does help protect against skin cancer.
• Randomized controlled trial data shows that daily sunscreen use reduced the occurrence of invasive melanoma by about 73%.

Sunscreen can give some people a false sense of safety. They might apply sunscreen in the morning and never reapply as they spend the day in the sun. But you need to reapply about every two hours or as often as the product packaging calls for.

People also tend to apply too little. For the whole body, the average adult needs about a shot glass’ worth of sunscreen.

You might ask, “What about the chemicals in some sunscreens that research shows can be absorbed into the bloodstream?”

Some older chemical UV filters can reach detectable levels in the blood after repeated applications. However, detectable doesn’t necessarily mean dangerous, and these ingredients haven’t been shown to cause cancer in humans.

We’re continuing to see better sunscreen technology become available. One example is bemotrizinol, or tinosorb S, which was recently approved by the FDA after being used in Europe for years.

If you want to avoid chemical sunscreens, choose a mineral sunscreen. Their ingredients are less likely to be absorbed into the bloodstream.

Myth: Sunscreen keeps us from the vitamin D we need

Broad-spectrum sunscreen blocks UVA rays as well as the UVB rays that our skin needs to produce vitamin D. But most people need only a little sunlight to maintain healthy vitamin D levels. During summer months in the United States, about 15 minutes of sun on the face and arms a couple of times a week is usually enough for adequate vitamin D production.

If your vitamin D level is low, it’s much safer and easier to get additional vitamin D from a supplement and from food than from skipping sun protection.

Myth: Sunburns aren’t a big deal

One sunburn isn’t likely to lead to serious health consequences. But reddening and even tanning is how your body shows that DNA damage has occurred from exposure to the sun’s ultraviolet (UV) light.

Sun damage accumulates over a lifetime, and that’s how skin cancers develop. A burn from your younger years might not have greater consequences for another 20 or 30 years, but research shows a clear link between sunburns and cancer.

Myth: Sunscreen contains harmful microplastics

Some sunscreens do contain synthetic polymers. Many daily facial sunscreens, particularly those made by cosmetic companies, include these ingredients, such as acrylate copolymers, dimethicone and polyethylene, to improve the way the product feels.

The polymers aren’t only found in sunscreen, though – they’re in moisturizers, makeup and other skin care products. And the polymers in sunscreens are too large to be absorbed through intact skin.

If you prefer to avoid these ingredients, you can opt for mineral-based “clean label” sunscreens that don’t rely on polymers.

Myth: People with darker skin don’t need sunscreen

Darker skin does provide more natural protection against UV damage. But ultraviolet rays can damage any skin. People with darker skin have much lower rates of melanoma and other skin cancers, and when melanoma does occur, it’s often found in areas that aren’t strongly related to sun exposure, such as the palms, soles or nails.

Lower risk doesn’t mean zero risk. People with darker skin can still get sunburned or develop skin cancer. And long-term sun exposure can also visibly age their skin faster.

I often tell patients to think of darker skin as having a built-in SPF of about 10. It’s helpful protection, but not enough for long sun exposure, especially during the summer or when you’re closer to the equator.

Myth: Sunscreen doesn’t work on me, because I still burn

I hear this from patients all the time, and usually it’s a misunderstanding of how sunscreen is supposed to work.

Many people wear sunscreen only on vacation, when they’re suddenly spending all day outside in sunnier locations than they’re used to. If they burn, they may naturally conclude the sunscreen didn’t work, but the sunscreen might have even prevented a much worse sunburn.

Again, make sure you apply enough sunscreen and reapply often. Pay attention to how you use spray sunscreen, especially – if you’re standing several feet away and giving yourself a quick mist, you’re probably not getting enough. Hold the can close to the skin, apply a generous layer, and rub it in to make sure it’s evenly distributed.

Sunscreen wears off over time and when you sweat or get wet. Even “water-resistant” sunscreen should be reapplied after swimming and about every two hours while you’re outdoors.

Finally, people can also misunderstand SPF. The SPF number, or sun protective factor, shows how much longer it takes UV rays to cause a sunburn than on skin without sunscreen. SPF doesn’t make you immune to the sun, and you can still burn spending a full day in strong sun, especially if you aren’t applying enough sunscreen or reapplying regularly.

That’s why sunscreen should never be your only strategy. It works best when combined with shade, hats, sunglasses and sun-protective clothing, particularly during the middle of the day, when UV levels are highest.