Don't get burned by your sunscreen

We found that you can't always rely on a sunscreen's SPF number

Consumer Reports magazine: July 2013

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Some sunscreens don’t keep sunburn at bay for as long as they promise. Our tests of 12 products showed that you can’t always rely on the SPF number, a measure of protection from burning UVB radiation. As a result, it’s especially important to check our Ratings for a sunscreen that did the job. Our key findings:

  • Against UVB rays, All Terrain AquaSport SPF 30 and Badger Unscented SPF 34 were poor. Against UVA rays, All Terrain was just fair. UVA penetrates deeper than UVB, tanning and aging skin, but both types can cause skin cancer.
  • Six sunscreens were very good overall. They guarded against UVB before and after 80 minutes under water and were very good against UVA when tested on people.
  • Four tested products contain nanoparticles of titanium dioxide, zinc oxide, or both. Those tiny particles help white lotion disappear on skin, but scientific studies continue to raise questions about their safety.
  • Paying more may not buy more protection. The least effective sunscreens were among the priciest.

How effective?

All things being equal, if you sunburn in 20 minutes without sunscreen, an SPF 30 product should protect your skin for about 10 hours (20 minutes times 30). In reality, the amount applied, sun intensity, your location, and your skin type make SPF simply a relative measure of protection. And as we found, it’s one you can’t always trust.

Our current tests found a bigger gap between many products’ claimed SPF and their actual SPF than we’ve found in the past. (In fact, a top-rated sunscreen from last year was All Terrain, the lowest-rated this year.) It’s hard to explain the changes. New labeling and test requirements from the Food and Drug Administration could have led sunscreen makers to tweak ingredients, but All Terrain and several other manufacturers told us they hadn’t changed formulations since our last tests. In any case, changes are difficult to pinpoint because formulas are proprietary.

How safe?

Skin cancer is the most common cancer in the U.S., and the benefits of sunscreens outweigh potential risks from their ingredients. That said, animal studies have raised some concerns.

Nanoparticles of titanium dioxide and zinc oxide have been linked to reproductive and developmental effects in animals. All Terrain AquaSport SPF 30, Badger Unscented SPF 34, and Kiss My Face SPF 40 claim to have no nanoparticles, but our tests showed that all had some. So did California Baby SPF 30+, whose website mentions “coated, micronized” particles.

Retinoids, part of the vitamin A family and an inactive ingredient in some sunscreens, have caused an increase in skin cancers in mice. There’s also a risk of birth defects in people taking oral acne medications containing retinoids, though they differ from the retinoids in sunscreens. As a precaution, pregnant women may want to choose a sunscreen without the ingredient retinol or retinyl palmitate.

Animal studies have indicated that oxybenzone, which is in many sunscreens, may interfere with hormones in the body.

The jury is still out on any harm from inhaling spray sunscreens. Until the FDA releases results of an ongoing study, avoid using sprays on kids, and spray sunscreen onto your hands before applying it to your face. Sprays are flammable, so let them dry before going near an open flame.

Bottom line

If you can’t find a recommended sunscreen, buy one that claims broad-spectrum protection, is water resistant, and has a claimed SPF of at least 40. We used to recommend 30, but given the performance of this latest batch, a claim of 40 makes more sense.

To use sunscreen properly and get the most protection from the sun, follow these tips:

  • Put sunscreen on 15 to 30 minutes before you head out into the sun. Most creams take more than 30 seconds to rub in.
  • For lotions, use at least 2 to 3 tablespoons to cover your body. For sprays, apply as much as can be rubbed in, then repeat.
  • Reapply all sunscreen, regardless of its SPF, every 2 hours and again after you swim or sweat, since sunscreen can rub off or wash off during the day. (Some leave a residue on skin. Most sunscreens left stains that didn’t wash out of cotton, polyester, and rayon/spandex.)
  • Limit your time in the sun, and if possible, wear protective clothing, a hat, and sunglasses.
  • Check the expiration date. The FDA requires manufacturers to provide an expiration date or show that a product will remain stable (but not necessarily maintain its SPF) for at least three years. If you buy an undated sunscreen, mark the purchase date on the container and, to be prudent, toss it once it’s two years old.
  • Don’t store sunscreen in a hot car—it may degrade faster. And skiers take note: Once frozen, sunscreens may lose effectiveness.

How we test sunscreens

Alas, there are no trips to Tahiti for our sunscreen panelists—they go to a lab. A sunscreen's score is based primarily on how well it protects against UVB and UVA radiation. But we look at other factors, too.

UVB protection: In UVB tests, five spots on one rectangular sunscreened area of the panelists’ backs are exposed for set times to rays from a sun simulator. After panelists have soaked in a tub of water, five spots in a second rectangular sunscreened area of their back are exposed in the same way. About a day later, the 10 spots are examined for redness. The resulting UVB Ratings reflect each product’s actual effectiveness, not how close it came to meeting its SPF claim.

UVA protection: To test for UVA protection, we also use people but check for tanning instead of redness.

Broad-spectrum protection. We use a test based on the Food and Drug Administration’s “critical wavelength” test, required for sunscreens that claim broad-spectrum protection. It assesses how well UV rays are absorbed by clear plastic plates treated with sunscreen. All products passed this test.

Staining: To test for staining, we apply each sunscreen to cloth swatches, let those dry, put them through two wash cycles, air-dry them, then check for stains.

Scent and skin feel: Finally, we have our trained sensory panel evaluate the scent and skin feel of the products.

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