Sunscreen Facts and Myths

Sunscreen advice has changed substantially over the years, and some older claims are still repeated as fact. Here are some of the most common sunscreen myths, with the current evidence put into context.

Myth: Sunscreen completely blocks vitamin D production

Fact: Sunscreen can reduce the amount of ultraviolet radiation reaching the skin, so in theory it can reduce vitamin D production. That does not mean people should deliberately expose unprotected skin to UV radiation in order to obtain vitamin D.

The American Academy of Dermatology recommends obtaining vitamin D through diet, fortified foods and supplements when needed rather than increasing UV exposure. Anyone concerned about vitamin D levels should discuss this with a healthcare professional.

Myth: People with dark skin do not need sun protection

Fact: Melanin provides some natural protection, but people of every skin tone can experience UV damage and develop skin cancer. Sun-protection choices should take into account UV levels, time outdoors, clothing coverage and individual risk rather than assuming darker skin is immune to UV injury.

Myth: SPF 30 gives twice the protection of SPF 15

Fact: SPF does not increase in a simple straight line. Under test conditions, SPF 15 filters about 93% of UVB, SPF 30 about 97% and SPF 50 about 98%.

Another useful way to look at the numbers is that SPF 30 allows roughly 1/30 of the relevant UV exposure through while SPF 50 allows roughly 1/50. Higher SPF therefore still provides greater protection, even though the difference looks small when expressed as a percentage.

Read more about how SPF ratings work.

Myth: SPF tells you how many hours you can safely stay in the sun

Fact: SPF measures relative protection from sunburn under controlled testing conditions. It is not a countdown clock.

UV intensity changes with the time of day, season, altitude, latitude, cloud cover and reflection from surfaces such as water and snow. Sunscreen can also rub off or be removed by swimming and sweating.

Myth: Every sunscreen automatically protects against both UVA and UVB

Fact: SPF primarily indicates protection against UVB-related sunburn. Look for a product labelled broad spectrum, or the equivalent UVA-protection designation used in your country, when protection from both UVA and UVB is required.

Myth: A thin layer is enough as long as you use sunscreen

Fact: The amount applied matters. Sunscreen testing uses a defined amount of product, and people commonly apply less than that in real life.

For an average adult, approximately 30-35 mL is commonly recommended for full-body coverage. Apply generously and evenly to exposed skin, and follow the directions on the product label.

See our sunscreen application tips.

Myth: Waterproof sunscreen lasts all day

Fact: There is no truly waterproof sunscreen. In the United States, water-resistance claims are based on testing for either 40 or 80 minutes in water. Other countries have their own testing and labelling standards.

Sunscreen should still be reapplied according to the label, particularly after swimming, sweating or towel-drying.

Myth: You cannot get UV damage on a cloudy day

Fact: Clouds do not block all ultraviolet radiation. UV exposure can still be significant on overcast days, and reflective surfaces such as water, sand and snow can increase exposure.

Use the local UV Index rather than visible sunshine alone to judge when sun protection is needed.

Myth: Sunscreen alone prevents all skin cancer

Fact: Regular sunscreen use can reduce UV damage and has been shown to reduce the risk of some skin cancers, but no sunscreen provides complete protection.

Sunscreen works best as part of a broader approach that can include shade, clothing, hats and sunglasses. Avoiding tanning beds is also important.

Myth: Sunscreen ingredients are proven to be more dangerous than UV exposure

Fact: Sunscreen regulation is more complicated than that claim suggests. Regulatory authorities continue to evaluate active ingredients and permitted filters vary between countries.

In the United States, the FDA has said that requests for additional safety data on some sunscreen ingredients should not be interpreted as a conclusion that those ingredients are unsafe. Zinc oxide and titanium dioxide have extensive safety data, and in June 2026 the FDA also added bemotrizinol to the U.S. over-the-counter sunscreen monograph.

If you prefer a mineral sunscreen or have sensitive skin, products based on zinc oxide or titanium dioxide are reasonable options. Learn more on our sunscreen ingredients page.

The practical bottom line

• Choose broad-spectrum protection.
• Use an SPF appropriate to current guidance in your country; SPF 30 or higher is commonly recommended.
• Apply enough sunscreen and reapply it.
• Use water-resistant sunscreen for swimming or heavy sweating.
• Do not rely on sunscreen as your only form of UV protection.

This page provides general educational information and is not a substitute for medical advice.

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