The short answer
Sunscreen helps protect skin from ultraviolet rays that can cause skin cancer. Choose a broad-spectrum product (CDC says SPF 15 or higher), use plenty, and reapply at least every two hours. Sunscreen is one layer of protection, along with shade and clothing.
Look for broad-spectrum sunscreen. CDC says SPF 15 or higher.
Most people apply too little; use a generous amount on all exposed skin.
Reapply at least every 2 hours, and more often if you swim or sweat.
Sunscreen has limits — it should be used with shade and clothing, not instead of them.
Watch: Does sunscreen cause cancer?
56 sec · Captioned · No good evidence sunscreen causes cancer — UV is the proven risk.
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Educational only — this video explains general report language and is not medical advice. Only your care team can say what a result means for you.
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The whole article, with every detail and caution.
The simple version
This page is for anyone choosing a sunscreen for themselves or their family. It covers labels, how much to use, and what sunscreen can and cannot do.
Sunscreen helps shield your skin from ultraviolet (UV) rays. CDC says most skin cancers are caused by too much exposure to UV rays. Used well, sunscreen is a simple part of protecting your skin.
It works only if you pick a suitable product, put on enough, and reapply. It is one layer among several, not the only thing between you and the sun.
Choose broad-spectrum, use plenty, and reapply often.
Reading the label
- Broad-spectrum. FDA says broad-spectrum sunscreens help protect against both UVA and UVB.
- SPF. FDA says SPF values mainly show UVB protection. CDC advises SPF 15 or higher. Ask your care team if you need more, for example because of your history or medicines.
If you will be swimming or sweating, look for a water resistant label. FDA requires it to state whether protection lasts 40 minutes or 80 minutes in the water. It is not forever.
No sunscreen blocks 100 percent of UV rays.
How much to apply
Using too little gives you less protection.
- FDA says an average-sized adult or child needs at least one ounce, about a shot glass, to cover the body from head to toe.
- FDA advises applying 15 minutes before sun exposure so it has time to work.
Reapplying
- FDA says to reapply at least every two hours, and more often if you are swimming or sweating.
- CDC also lists after toweling off.
A phone reminder or a bottle in your bag can help.
Sunscreen is one layer
CDC also lists other ways to cut sun damage:
- Stay in the shade under an umbrella, tree, or other shelter.
- Wear tightly woven clothing.
- Wear a hat with a brim all the way around.
- Wear sunglasses that block both UVA and UVB.
Sunscreen is a teammate to these steps, not a replacement.
Storage and expiration
FDA says a sunscreen with no expiration date should be treated as expired three years after purchase. If yours has a date that has passed, replace it.
Sprays
FDA notes safety concerns with spray sunscreens, including fire risk from the alcohol in some. Follow the label directions.
Children
FDA says sunscreen is not recommended for infants under six months old. Ask your child's care team how to protect a baby from the sun.
Sources
- FDA: Sunscreen: How to Help Protect Your Skin from the Sun (fda.gov)
- CDC: Sun Safety (cdc.gov/skin-cancer)
Common questions
What does broad-spectrum mean?
Broad-spectrum means the sunscreen helps protect against both UVA and UVB rays, the two forms of UV radiation.
What SPF should I choose?
CDC says to use broad-spectrum sunscreen with an SPF of 15 or higher. SPF values mainly show protection against UVB. No sunscreen blocks 100 percent of UV. Ask your care team if you need more protection.
How much sunscreen should I use?
FDA says an average-sized adult or child needs at least one ounce, about what it takes to fill a shot glass, to cover the body from head to toe. Using less gives you less protection.
How often do I need to reapply?
FDA says to reapply at least every two hours, and more often if you are swimming or sweating. CDC adds after toweling off. A water resistant label must state whether it lasts 40 or 80 minutes in the water.
Does sunscreen expire?
FDA says a sunscreen with no expiration date should be considered expired three years after purchase. If yours has a printed date that has passed, replace it.
Is spray sunscreen as good as lotion?
FDA notes safety concerns with spray sunscreens, including that some contain alcohol and can catch fire. Read the label directions and keep sprays away from flames and heat.
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Last updated: 2026-10-02Next planned review: 2027-07-04
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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