Sunscreen: Answering Your Questions

After my recent entry debunking sunscreen myths, you raised many excellent questions.

Indeed, sun protection can be a confusing area of skin care, but it's an area that we owe it to ourselves to sort through - about 50,000 cases of melanoma and 1 million cases of non-melanoma skin cancer will be diagnosed in the United States this year. Let's consider some of your most common questions:

Is it true that there's no such thing as an SPF above 15?
SPF, or sun protection factor, describes how much longer protected skin can resist reddening than unprotected skin - if you're wearing SPF 15, then, you can theoretically spend 15 times longer in the sun without burning.

It's true that there is a minimal difference in coverage between SPF 15 and, say, SPF 45 if you apply the appropriate amount of each. But studies have shown that most people apply about one-quarter of the sunscreen they should, and get only 20-50 percent of the SPF they think they're getting.

For the record, you should apply about a quarter-size amount to your face, neck, and chest - use that as a gauge for the rest of your body. That's why higher SPFs are so valuable: Even if you don't apply enough, you're still better protected than you'd be if you used lower SPF. But you still need to reapply - every hour during direct sun exposure!

Why is it that our ancestors never used sunscreen and were fine?
Unfortunately, we are living on a different planet than even our parents and grandparents were - the ozone layer is much thinner than it was, leaving us exposed to increasingly high amounts of the sun's ultraviolet rays. Furthermore, as life expectancy climbs, we are seeing medical conditions that simply didn't have time to develop hundreds or thousands of years ago.

What is "unstable" sunscreen and how can I avoid using it?
You've probably heard the term "unstable" in reference to the new generation of UVA-blocking sunscreens. Avobenzone was the first chemical UVA blocker approved in the United States, but it was initially hard to stabilize and broke down after 30-60 minutes of sun exposure.

Since then, however, companies have stabilized avobenzone to last several hours and another UVA blocker, Mexoryl, has also been approved by the FDA. The best way to avoid older, unstable sunscreen is to throw away any products more than six months old.

What's the difference between physical and chemical sunscreens? Are chemical sunscreens safe?
In a nutshell, physical sunscreens protect skin by reflecting light, whereas chemical sunscreens protect skin by absorbing radiation and then dissipating it safely.

Yes, chemical sunscreens are safe and undergo rigorous testing before they are allowed on the market. They are absorbed by the skin and secreted in the urine, however, versus physical sunscreens that stay on the skin's surface.

As a result, women who are pregnant or breast-feeding should avoid chemical sunscreens, and I recommend using physical sunscreen on children under five. Physical sunscreens are also an excellent option if you have sensitive skin or simply prefer to avoid chemical products.

But if I wear sunscreen, aren't I missing important opportunities to naturally produce vitamin D?
All of you who pointed out the importance of vitamin D are absolutely right, and recent studies have indeed suggested that we may not be getting enough of it.

However, please be aware that the amount of sun exposure required to boost vitamin-D levels is a mere 15 minutes. In the dermatological community, we fear that people will use the latest vitamin-D studies as a license to bake in the sun all day, which remains very dangerous for your skin. Furthermore, although in lower amounts, vitamin D is widely available in food and supplements.

Wishing you great skin!

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Dr. Baumann is author of the best-selling book, " The Skin Type Solution." To learn more about her revolutionary skin typing system, visit her Web site,

All of Dr. Baumann's recommended skin care products are available online, and a portion of proceeds goes to The Dermatology Foundation.

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