Is it true that there's no such thing as an SPF above 30 - are the higher numbers just a marketing ploy?
Higher SPFs do offer more protection than lower SPFs, even above 30 - but you're right that sunscreen rarely offers as much protection as you think. That's not the fault of the manufacturer or the result of some advertising scheme, though. It's actually because the average person applies far less sunscreen at a time than he or she should.
To measure a product's SPF, researchers assume that users will apply 2 mg per cm2 of skin - for the face, for example, that translates to about half a teaspoon. The trouble is, studies show that most people use about ¼ of that amount. So while the difference in protection between an SPF 15 and an SPF 45 might be minimal when you use the requisite amount of each, the SPF 45 offers much better protection if you skimp (and chances are, you're skimping!).
In a nutshell, I always recommend that patients use the highest SPF they can stand - it's a good way to make up for the discrepancy between what we apply and what we should apply.
If I put on sunscreen in the morning, am I still covered for my walk home from work 9 hours later?
Although you may have still some coverage - it's better than nothing -- it is best to reapply for your trip home. With time, the chemicals in sunscreen break down and lose their ability to absorb the sun's rays. (That's how chemical sunscreens work: They absorb UV rays and dissipate them safely, protecting your skin's structural proteins.) When you're in direct sunlight, it's an absolute must that you reapply every hour.
And even if you spend the day indoors, with no reapplication, there will be very little left of your morning dose by the time you walk home. Physical sunscreens that contain zinc and titanium dioxide may last longer than chemical sunscreens, however, reapplying is the only way to be sure that you have good protection.
While I urge you to reapply to be safe, remember that sunscreen isn't the only way to protect yourself. If you know you're simply not going to slather sunscreen on your face at the end of a day, consider investing in an elegant wide-brimmed hat.
Lately, I've been seeing more and more people using umbrellas to block the sun. Does the fabric on an average umbrella really block UV rays?
I have always loved this idea. It might strike some readers as excessive, but I often see women protecting their skin this way when I travel in Asia, where people tend to be particularly vigilant about sun avoidance.
However, not all umbrellas are created equal: the most important factor to consider is the tightness of the fabric's weave. The more space between threads, the more sun that fabric allows through. Dark fabrics will also better protect you than light ones. Not sure how much protection your umbrella offers? Hold it up to a light bulb. If you see a lot of light get through, then the sun's rays will, too.
But remember, avoiding the sun by creating your own shade is just part of a good sun-protection plan - umbrellas will generally only give you an SPF of 5-15, depending on the fabric. And light is also reflected off of water, concrete, and other shiny surfaces, meaning that not all sun is coming from above. Umbrellas aren't a license to skip sunscreen.
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, SkinTypeSolutions.com.
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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