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Cancer Risk and Prevention

How to Use Sunscreen

Sunscreen is found in various products that you put on your skin to protect it from the sun’s UV rays. But it’s important to know it’s called sunscreen for a reason and there is no such thing as sunblock. Sunscreen is just a filter – it does not block all UV rays.

When to apply and reapply sunscreen

  • Consider sunscreen as one part of your overall skin cancer protection plan, year-round, especially if staying in the shade and wearing protective clothing aren’t available as your first options.
  • Sunscreen should not be thought of as your first line of defense. Seeking shade and avoiding direct sunlight is most important.
  • Sunscreen should not be used as a way to prolong your time in the sun. Even with proper sunscreen use, some UV rays still get through.

Sunscreen needs to be reapplied at least every 2 hours to maintain protection. Sunscreen can wash off when you sweat or swim or when you dry off with a towel, so it might need to be reapplied more often. Some people may find they need to reapply sunscreen more often regardless of the activity they’re doing outside. Always be sure to read the label.

Even if you use a sunscreen with a very high SPF, this doesn’t mean you can stay out in the sun longer, use less sunscreen, or apply it less often. Again, always be sure to read the label.

How to put on sunscreen

Always follow the label directions for applying and re-applying sunscreen products. Most experts recommend applying sunscreen generously whether it’s your first time using it for the day or you’re re-applying it after a length of time.

When putting sunscreen on:

  • Pay close attention to your scalp (including hairline), face, ears, neck, arms, and any other areas not covered by clothing.
  • Don’t forget your lips. Use lip balm with sunscreen when possible.
  • When you wear insect repellent or makeup, put sunscreen on first.
  • Set an alarm or timer on your watch or phone to remind you to re-apply sunscreen at least every 2 hours or more frequently if needed.

How much sunscreen to use

Ideally, sunscreen should be applied generously. You might see instructions saying to apply liberally or generously. Or you might see a recommended amount to use. It’s important to use enough to have full coverage of arms, legs, neck, face, and any other areas that are exposed to the sun.

What type of sunscreen is best?

Sunscreens are available in many forms, including lotions, creams, ointments, gels, sprays, wipes, and lip balms. Some cosmetics, such as moisturizers, lipsticks, foundations, and other makeups are also considered sunscreen products if they have sunscreen as an ingredient. It’s important to remember that no sunscreen protects you completely.

Read sunscreen product labels

When choosing a sunscreen product, be sure to read the label. It’s best to use sunscreen with broad spectrum protection (against both UVA and UVB rays) and with sun protection factor (SPF) values of 30 or higher.

Some sunscreen products can irritate the skin. Some labels may provide information about how to test for skin irritation or sensitivity. If your skin becomes irritated, contact your doctor or a dermatologist for ideas about which type or brand might be best for you.

What does SPF mean?

The SPF number is the level of protection the sunscreen provides against UVB rays, which are the main cause of sunburn.

  • Sunscreens labeled with SPFs as high as 100+ are available.
  • In the US, sunscreens with an SPF lower than 15 must include a warning on the label stating that the product has been shown only to help prevent sunburn, not skin cancer or early skin aging.
  • A higher SPF number means more UVB protection.

When applying sunscreen correctly, you get the equivalent of 1 minute of UVB rays for a certain about of time you spend in the sun. The amount of time is based on the SPF level of the product. For example, a sunscreen with SPF 30 gives the equivalent of 1 minute of UVB rays for each 30 minutes you spend in the sun. This means 1 hour in the sun wearing SPF 30 sunscreen is the same as spending 2 minutes in the sun totally unprotected. Higher SPF numbers do mean more protection, but the higher you go, the smaller the difference becomes.

  • SPF 15 sunscreens filter out about 93% of UVB rays
  • SPF 30 sunscreens filter out about 97%
  • SPF 50 sunscreens filter out about 98%
  • SPF 100 filter out about 99%.

Broad spectrum sunscreen

Sunscreen products can only be labeled “broad spectrum” if they have been tested and shown to protect against both UVA and UVB rays. Sunscreens that help protect against UVA rays might include avobenzone (Parsol 1789), zinc oxide, and titanium dioxide.

Only broad spectrum sunscreen products with an SPF of 15 or higher can state that they help protect against skin cancer and early skin aging if used as directed with other sun protection measures.

Water resistant sunscreen

Sunscreens cannot be labeled as “waterproof” or “sweatproof” because these terms can be misleading. Sunscreens can claim to be “water resistant,” but they have to state whether they protect the skin for 40 or 80 minutes of swimming or sweating, based on testing.

Expiration dates

Check the expiration date on the sunscreen to be sure it’s still effective. Most sunscreen products are good for at least 2 to 3 years, but you may need to shake the bottle to remix the sunscreen ingredients. Sunscreens that have been exposed to heat for long periods, such as if they were kept in a glove box or car trunk through the summer, may be less effective.

Is sunscreen safe?

The US Food and Drug Administration (FDA) is required to monitor sunscreen since it’s considered a cosmetic. The FDA has very high standards during this process that are based on scientific research to be sure the product is safe for public use. The FDA looks at the ingredients in a sunscreen and how it is made to determine if the product is safe and effective.  If it is, the sunscreen is considered GRASE (generally safe and effective).

Currently, the FDA has not reported that any sunscreen ingredients used in the US are harmful to a person’s health. However, the FDA has recommended more research be done on certain ingredients that are often used in sunscreen products. The ingredients commonly used in the US that the FDA lists as needing more research are: ensulizole, octisalate, homosalate, octocrylene, octinoxate, oxybenzone, and avobenzone. You can read more about these ingredients at

Expert organizations consider sunscreen a safe, vital tool in the prevention of skin cancer. Along with the FDA, the American Cancer Society (ACS) and the American Academy of Dermatology Association (AAD) continue to include using sunscreen with SPF 30 or higher (along with wearing protective clothing, hats, and sunglasses) to protect your skin from harmful UV rays.

Can sunscreen harm marine life?

Not all sunscreen stays on your skin when it is applied. Swimming, showering, and sweating can cause sunscreen to wash off and go into waterways. Scientists have found that certain chemicals in some sunscreen products can harm coral reefs and other organisms in bodies of water.

Mineral sunscreen is a good option since it does not use the types of chemicals that can be harmful to marine life. Additionally, wearing UV protective clothing is a good option for protecting your skin when there is concern about sunscreen ingredients being harmful during water activities.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

American Academy of Dermatology (AAD). Is Sunscreen Safe? Accessed at on June 26, 2024. 

National Academies of Science, Engineering, Medicine (NASEM). Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health. 2022. Accessed at on June 26, 2024.

National Ocean Service. Skincare Chemicals and Coral Reefs. 2013. Accessed at on June 26, 2024.

US Food and Drug Administration (FDA). FDA Takes Steps Aimed at Improving Quality, Safety and Efficacy of Sunscreens. 2021. Accessed at on June 26, 2024.

US Food and Drug Administration (FDA). Sunscreen: How to Help PRotect Your Skin from the Sun. Accessed at on June 26, 2024.

Last Revised: June 26, 2024

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