Medical Edge Newspaper Column

Sunscreen Can Offer Great Protection, But Read Labels

May 16, 2008
Dear Mayo Clinic:
What do I need to know about sunscreen? And is it okay to use on my kids?

Answer:
When buying sunscreen, you'll want to determine the type of sun protection the product offers, the strength of the product, and how to apply it for best effect. Thanks to a recent mandate by the Food and Drug Administration (FDA), all sunscreen labels will clearly communicate this and more by May 2009, but in the meantime, look for key information.

Check for sunscreen that has the broadest spectrum of protection from ultraviolet light, those intense, invisible rays from the sun that damage our skin and lead to serious long-term consequences that include premature aging and increased risk of cancer.

Ultraviolet light is divided into three wavelengths — ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). Only UVA and UVB rays reach the earth. UVB rays are short wavelengths that affect primarily the topmost level of our skin, causing sunburn (erythema). The longer UVA rays penetrate deeper, darkening and aging our skin, altering its cell structure and weakening the skin's immune system.

Traditionally, sunscreen products have focused on UVB protection, which is identified by the SPF (sun protection factor) number on the label. The higher the SPF number, the greater the protection. But it's also important to be protected from damaging UVA rays. Sunscreen products that offer UVA protection will carry a one- to four-star rating system for UVA protection. A product that carries high ratings for both will offer you broad-spectrum coverage to better protect your skin.

But any sunscreen product is only as good as its application. Many studies have shown that people apply too little sunscreen and they don't reapply as often as they should. So you can buy an SPF 50+, but if you put a dime-size amount on your entire torso and then never reapply, you're not getting the sun protection factor you paid for.

The rule of thumb is an ounce of sunscreen for the average adult. That's enough to fill a shot glass. It should be worked in well before going out into the sun, and more of the product should be applied every couple of hours, more often if you get wet or sweat.

Sunscreens have a physical or chemical base. Physical-block sunscreen contains natural compounds that form an opaque film that reflects or scatters ultraviolet light before it can penetrate the skin. Such products contain either zinc oxide or titanium dioxide, both of which protect against UVA and UVB rays.

Chemical-block sunscreens work by absorbing or reflecting UV rays. Many of these products combine several synthetic ingredients to ensure broad-spectrum protection. Because chemicals breakdown over time, chemical-based sunscreens carry an expiration date. It's best to review your inventory of sunscreens once a year.

If your skin reacts to a certain brand, don't just stop using sunscreen. Check the label and buy a sunscreen with different active ingredients (many combinations are available). Look for sunscreen that is user friendly. You're much more likely to use it if you like the way it feels on your skin. Manufacturers are moving away from slick, oily and heavily perfumed sunscreens to lightweight formulas that blend more easily.

In addition to sunscreen, use other methods to help you enjoy the outdoors while avoiding harmful ultraviolet rays. Protective clothing is a good start, but remember that not all clothing is SPF equal. For example, a cotton T-shirt may seem like a good cover-up, but it provides only SPF 4 protection. Ultraviolet protective factor (UPF) clothing is made with a tighter weave to block more light. It is available in retail stores and online. And a UPF laundry rinse can boost protection for your other clothes.

Children have vulnerable skin and should be protected from the sun, preferably through the use of sunscreen and protective clothing and avoidance of peak hour exposure (10 a.m. to 4 p.m.). However, do not use sunscreen on infants under six months of age. Instead, keep babies in the shade, and use clothing and hats to protect their skin.

For everyone else, be aware of the time you spend in the sun, especially those peak hours. And remember that even if the sky is overcast, the sun can burn and damage your skin. Take time outs from sun exposure. Seek shade. And finally, don't forget to use a broad-brimmed hat as well as UVA/UVB-rated sunglasses to protect your eyes.

— Dawn Davis, M.D., Dermatology, Mayo Clinic, Rochester, Minn.