What's Your SPF IQ?

[P.J. Lurvey]

NPR’s recent post What’s your IQ on SPF?encouraged me to wonder what my SPF IQ is… And what percentage of my sunburns could have been avoided had I known better. After some digital research on dangers of sun damage, the myths of sun block, and the consumerization of skin care, I have uncovered some interesting findings.

Skin cancer is the most common type of cancer and sun damage is responsible for 90 percent of non-melanoma cases. Likely, sun damage is high because of the myths that lead to inappropriate sun block usage—one being the damage is already done and another, if you have a strong base you don’t need sun block.

But here is a new myth that I recently learned…. SPF 100 is better than SPF 75.  On a recent beach trip, I overheard one woman say “Do you have SPF 100? It’s the only thing that works.”

SPF 100? Is that necessary?

As background, 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.

SPF 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 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.

Sunscreens with higher SPF ratings block slightly more UVB rays, but none offers 100% protection.

In a written statement, Neutrogena noted, “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.”

Say what, Neutrogena? The difference in skin protection between an SPF 55 and SPF 100+ may be slightly less than 1%... If sunbathers have to reapply sunscreen regardless (because nothing blocks sun 100%), why spend millions in R&D and product marketing for something that seems inconsequential?

Answer: Profit. And the power of marketing. In a recent price comparison, three ounces of Neutrogrena SPF 60 cost $10. The same amount of Neutrogena SPF 100 -- $17.00

SPF 100+ barely protects the skin any more than SPF 55, and yet consumers are clamoring for the higher SPF—despite the markup.

So here are three final lessons:

(1)Do your homework as a consumer.

(2) Repeat applications of 30 or 60 work just as well as repeat applications of SPF 100 (while saving a buck).

(3) Repeat applications are key –nothing offers 100% protection.