Q: When it comes to sunscreen, is higher SPF always better?
A: Once SPF (sun protection factor) goes over 30, the increase in protection is negligible, according to the Skin Cancer Foundation. Not too long ago, SPFs went only as high as 15 or 30. But in recent years, sunscreen manufacturers have been in an arms race, marketing products with SPFs of 70 or 100 or even higher. Unfortunately, high SPFs can give people a false sense of security if they assume, say, that SPF 70 is more than twice as effective as SPF 30, which is far from true.
SPF refers primarily to a sunscreen’s ability to block the sun’s ultraviolet-B (UVB) radiation, the main cause of non-melanoma skin cancer and sunburn; ultraviolet-A (UVA) is mostly responsible for skin aging; both increase the risk of melanoma. When properly applied, a product with SPF 15 blocks 93 percent of UVB; SPF 30 blocks 97 percent; SPF 50 blocks 98 percent; SPF 100 blocks 99 percent.
To get those levels of protection, sunscreens have to be “properly applied.” That means generously applied and re-applied every two hours or after swimming or sweating heavily. In reality, people apply much less, on average, than is used in laboratory testing. So real-world effectiveness is far lower than 93 to 99 percent blockage of UVB.
One potential problem with super-high SPFs is that such products may block more UVB than UVA. Thus, they are better at preventing sunburn than lower SPFs, but don’t necessarily reduce other kinds of skin damage. In that case, people may think they’re protected because they aren’t turning red and thus will stay out in the sun longer or re-apply lotions less often. Indeed, some studies have found that vacationers tend to spend more time in the sun when given sunscreens with higher SPFs. That’s why some countries have capped SPFs at 30 or 50.
Our advice: Buy sunscreen labeled “broad-spectrum” or “UVA/UVB protection” with an SPF of at least 15—or at least 30 if you are very sensitive to the sun, have a personal or family history of skin cancer, or are spending long hours in intense sunlight. It’s not worth spending extra for super-high SPFs. Be sure to apply sunscreen generously (that may mean 2 ounces for your entire body) and often, and to take other sun-protective measures, such as wearing a hat and protective clothing.
Also see Sunscreen Myths vs Facts.