How to Choose a Sunscreen and Use It Well
Sunscreen labels are full of numbers and terms: SPF, broad spectrum, water resistant, mineral, chemical. It is easy to feel lost in the store. But the choice is simpler than it looks, and the way you use sunscreen matters as much as the bottle you buy.
This guide explains what the label words mean, which type I would choose, and how to apply it so it works. I also cover the spots people miss most often.
Medical Disclaimer
This article is provided for general educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. While the content is written with input from a licensed healthcare professional, reading this article does not create a nurse-patient, provider-patient, or any other professional relationship between you and the author or Vida Atlas.
The information here is general in nature and is not a substitute for personalized medical advice from your own doctor or qualified healthcare provider, who can take your full medical history and individual circumstances into account. Always consult your doctor or another qualified healthcare provider with any questions you may have regarding a medical condition, and never disregard professional medical advice or delay seeking it because of something you read on this site.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency room immediately. Do not rely on this article for urgent or emergency medical situations.
Vida Atlas and the author make no representations or warranties about the accuracy, completeness, or timeliness of the information provided, and disclaim liability for any actions taken or not taken based on the content of this article.
Key Takeaways
- Choose a sunscreen that says “broad spectrum” and has SPF 30 or higher.
- Most adults need about 1 ounce, the size of a shot glass, for the whole body.
- Apply 15 minutes before going outside, and reapply at least every 2 hours.
- No sunscreen is waterproof. Reapply after swimming or sweating.
- Shade, clothing, a hat, and sunglasses add protection that sunscreen alone cannot give.
What the Label Words Mean
The FDA explains that SPF, or Sun Protection Factor, measures protection against UVB rays, which mainly cause sunburn (1). SPF does not tell you how long you can stay in the sun (1). “Broad spectrum” means the product protects against both UVA and UVB rays (1).
“Water resistant” must state whether the protection lasts 40 or 80 minutes in water or while you sweat (1). No sunscreen is truly “waterproof” (1). So after swimming or heavy sweating, apply it again.
Which SPF to Choose
The FDA advises broad-spectrum sunscreen with SPF 15 or higher (1). The American Academy of Dermatology recommends SPF 30 or higher, together with broad-spectrum and water-resistant protection (2). I choose SPF 30 or higher, because it gives more protection, and I look for all three words on the label.
Higher numbers add less than people expect. SPF 30 filters out 97% of UVB rays, and higher numbers block only slightly more (4). No sunscreen blocks 100% (4). So it is better to use enough sunscreen of SPF 30 than a thin layer of SPF 100.
Mineral or Chemical?
The difference is in the active ingredients. If the active ingredient is zinc oxide, titanium dioxide, or both, it is a physical, or mineral, sunscreen (4). Dermatologists recommend mineral sunscreens for people with sensitive skin (4).
I pick a mineral sunscreen for my face and for anyone with sensitive skin. For the rest, I choose whichever type I will actually wear, as long as it says broad spectrum, water resistant, and SPF 30 or higher. The best sunscreen is the one you use every time. If you notice skin changes, see Skin Changes That Might Signal Something More.
How to Apply It
The FDA says an average adult needs about 1 ounce, the size of a shot glass, to cover the whole body (1). Apply it about 15 minutes before you go outside, and reapply at least every two hours, and more often if you swim or sweat (1). Most people use far too little, which lowers the protection a lot.
The FDA also lists the places that are often missed: ears, nose, lips, the back of the neck, hands, tops of the feet, the hairline, and the scalp (1). Use a lip balm with SPF for your lips. Harvard Health says it is harder to know that you covered all your skin with a spray, and that breathing in the spray could be harmful (3). I prefer lotion for that reason.
Sunscreen Is Not the Only Protection
The FDA advises limiting time in the sun between 10 a.m. and 2 p.m., when rays are strongest (1). It also suggests long sleeves, pants, sunglasses, and a broad-brimmed hat (1). The American Academy of Dermatology notes that up to 80% of harmful UV rays can pass through clouds (4), so cloudy days still count. Sunscreen works best as one layer of protection among several.
Check the Expiration Date
The FDA says not to use sunscreen after its expiration date (1). If there is no date, treat it as expired three years after you bought it, and if you do not know its age, throw it away (1). Keep it out of direct sun and heat (1). Do not leave a bottle in a hot car.
Products That Can Help
Here is what to put in your bag. Buy the type you will use every day, not the one with the most claims.
A Daily Face Sunscreen
I pick a broad-spectrum lotion with SPF 30 or higher that feels light on the skin and does not sting your eyes. A mineral type is a good choice for sensitive skin (4).
A Water-Resistant Body Sunscreen
For beach days and sports, choose a water-resistant lotion, and check whether it says 40 or 80 minutes (1). Buy a large bottle, so you are not tempted to use too little.
A Lip Balm With SPF
Lips are easy to forget and burn quickly. Keep one in every bag and coat pocket.
A Wide-Brimmed Hat
Choose a hat with a brim that goes all the way around, because it shades the face, ears, and neck (1).
Sunglasses
Choose sunglasses that say they block UV rays, with lenses that wrap a little at the sides.
Common Mistakes to Avoid
Using Too Little
A thin layer gives much less protection than the label says. Use about a shot glass for the body (1).
Applying Only Once
Sunscreen wears off. Reapply at least every two hours (1).
Skipping Cloudy Days
Up to 80% of harmful UV rays can pass through clouds (4). Wear sunscreen on cloudy days too.
Using Old Sunscreen
Check the date. Old sunscreen may not protect as well (1).
Try This Week
Small steps make a big difference over time:
- Check the date on every sunscreen you own.
- Put a bottle by the door, so you see it before you leave.
- Apply sunscreen to your face every morning for seven days.
- Check your ears, neck, and the tops of your feet next time you apply it.
Final Thoughts
A good sunscreen is broad spectrum, SPF 30 or higher, water resistant, and one you will actually use. Apply enough, apply it early, and apply it again. Add shade, clothing, and a hat for stronger protection. If you notice a mole or spot that changes, ask your doctor to look at it.
