By Salynn Boyles
Reviewed by Louise Chang, MD
If you’ve shopped for sunscreen lately, you have probably noticed the proliferation of products with ever-higher sun protection factor (SPF) ratings.
Just a few years ago, it was hard to find a sunscreen claiming an SPF higher than 45. These days, the shelves are lined with products from companies such as Banana Boat, Coppertone, and Aveeno touting SPF ratings of 70+, 80, and 90+. Neutrogena recently introduced Ultra Sheer Dry-Touch Sunblock SPF 100+. But is a 100+ or a 90+ sunscreen really that much better than one with an SPF of 15?
SPF 100: Twice as Good As SPF 50?
SPF refers to the ability of a sunscreen to block ultraviolet B (UVB) rays, which cause sunburns, but not UVA rays, which are more closely linked to deeper skin damage. Both UVA and UVB contribute to the risk of skin cancer.
It is a measure of the time it would take an individual to burn in the sun if they were not wearing sunscreen vs. the time it would take with sunscreen on.
“SPF is not a consumer-friendly number,” says Florida dermatologist and American Academy of Dermatology (AAD) spokesman James M. Spencer, MD. “It is logical for someone to think that an SPF of 30 is twice as good as an SPF of 15, and so on, but that is not how it works.”
According to Spencer, an SPF 15 product blocks about 94% of UVB rays, an SPF 30 product blocks 97% of UVB rays, and an SPF 45 product blocks about 98% of rays.
“After that, it just gets silly,” he says.
Sunscreens with higher SPF ratings block slightly more UVB rays, but none offers 100% protection.
Spencer says SPF 15 sunscreens are fine if used correctly, but he recommends SPF 30 products to his patients because few people apply sunscreens as heavily or as often as they should.
Farah Ahmed, who is general council for the cosmetics industry group Personal Care Products Council, concedes that the difference in sunburn protection between the medium- and high-SPF sunscreens is not great.
But she says the high SPF products may better protect against long-term skin damage and exposure-related skin cancers.
In a written statement, Neutrogena notes that because most people use far less sunscreen than is recommended, high SPF sunscreens can offer better protection.
“Higher SPFs used over a lifetime may translate to healthier skin in later life,” the statement reads. “While the difference in the percentage of ultraviolet radiation blocked between an SPF 55 and SPF 100+ may be slightly less than 1%, applying an SPF 100 may lead to much less cumulative sun damage over a lifetime.”
What about UVA Rays?
Finding a sunscreen that adequately protects against UVA rays is much trickier, but every bit as important. UVA radiation reaches deeper into the skin and contributes to wrinkles and skin cancer risk. Nearly all (95%) of the UV radiation that we are exposed to is UVA radiation.