What is the correct way to use sunscreen?
The topic of sunscreen use is ripe with controversy and misconceptions. Some authorities advocate against their use, believing that too little sun exposure will reduce the body’s vitamin D levels with the increased risk of osteoporosis and certain cancers (breast, colon, and prostate). The American Academy of Dermatology, on the other hand, strongly recommends sun avoidance practices including use of sunscreens to reduce the risk of developing skin cancer.
Here are a few of the common misconceptions regarding the use of sunscreens preventing skin damage from sunburn:
Misconception #1 – The SPF is an indication of sunscreen protection across the entire ultraviolet light spectrum. The sun emits two types of ultraviolet light—UVB, which causes sunburn and can lead to skin cancer, and UVA, which causes wrinkles and deeper skin damage that can also lead to skin cancer. Most people know that SPF stands for sun protection factor. What is less well known is that this is a measure of how well the sunscreen deflects UVB rays only. Sunscreens that pass the Federal Drug Administration’s (FDA) broad spectrum test, however, will have demonstrated that they also provide UVA protection that is proportional to their UVB protection.
Misconception #2 – The higher the SPF, the better. SPF values displayed on sunscreen labels range from 2 to as high as 50 (or higher). This refers to the product’s ability to screen or block out the sun’s harmful rays. Theoretically, a sunscreen with SPF 15 will allow you to be in the sun 15 times longer than you could without sunscreen before becoming sunburned. Protection from sunburn, however, does not increase proportionally with an increased SPF number. A SPF of 2 will absorb 50% of ultraviolet radiation, an SPF of 15 absorbs 93% and an SPF of 34 absorbs 97%. No sunscreen can block 100% of the sun’s rays.
Misconception #3 – Waterproof sunscreens stay on even when swimming. There is no such thing as “waterproof” sunscreen. The FDA even prohibits manufacturers from labeling sunscreens as “waterproof” because these claims overstate their effectiveness. Sunscreens can be labeled as being “water resistant” if they maintain their SPF rating after 40 to 80 minutes of water exposure. Most sunscreens will not maintain their SPF rating after swimming or sweating heavily for much more than an hour.
Misconception #4 – Sunscreens are so concentrated that a thin coating is all that’s necessary. Most people do not use adequate amounts of sunscreen. Studies have shown that people apply only about 25-50% of the amount required to reach the labeled SPF rating.
Misconception #5 – Vitamin A added to sunscreen is important for skin health. It’s true that Vitamin A added to sunscreen will help hydrate skin and prevent skin degradation. Data from an FDA cancer study, however, showed that Vitamin A in a synthetic form called retinyl palmitate may also speed the growth of skin tumors.
Recommendations for effective sunscreen use. The ideal sunscreen would completely block all UV rays, remain effective on the skin for several hours, and not cause skin irritation. Unfortunately, the ideal sunscreen does not yet exist. Here are some tips for the more effective use of the sunscreens that are currently available.
- For most people, a sunscreen with a sun protection factor (SPF) of 15-30 will provide adequate protection.
- Look for sunscreen that says that it provides “broad spectrum” protection. Broad spectrum protection means that it has both UVA as well as UVB blocking properties.
- Perhaps more important than the SPF rating is appropriate application and reapplication of sunscreen. Be sure to apply sunscreen at least 15-30 minutes before exposure to the sun. Follow the guideline from the American Academy of Dermatology— “one ounce, enough to fill a shot glass”, is the amount needed to cover exposed areas of the body. This amount should be adjusted depending on body size and the amount of exposed skin. “Water resistant” sunscreens need to be reapplied every 1 to 2 hours when swimming or sweating heavily.
- If you are extremely UV-sensitive, get a sunscreen with an even higher SPF rating. For all intents and purposes, a sunscreen rated 50+ is as high as anyone needs.
- For maximum protection against UV rays, use a sunblock rather than sunscreen. These contain physical agents, such as titanium dioxide or zinc oxide keep UV rays from reaching the skin.
- One of the best ways to protect your skin from cancer and premature aging is by limiting sun exposure and wearing protective clothing. Avoid sun exposure between 10 AM and 4 PM, the time that UV radiation is at its highest. Remember also that UVA radiation is not significantly lower during morning hours or on overcast days.
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