Safe and effective use of sunblock, or sunscreen, is key to preventing damage from the sun's rays. You will increase your chance of developing skin cancer by leaving your skin unprotected while exposed to the sun. The sun causes more than 1 million cases of nonmelanoma skin cancer diagnosed in the U.S. each year, according to the American Cancer Society. For optimal protection, the American Academy of Dermatology recommends purchasing a sunblock that protects against both ultraviolet A and ultraviolet B rays.
How It Works
Sunblock protects your skin from the sun's dangerous rays by reflecting and absorbing ultraviolet A and ultraviolet B light, according to the University of California, San Francisco School of Medicine Department of Dermatology. How long a sunblock will be effective at protecting you from the dangerous effects of the sun depends on its sun proof factor, or SPF, a number given to every sunscreen that indicates for how long it can prevent sunburn.
Choosing an SPF
Which level of SPF that you need depends on your skin type, how long you will be in the sun and what you will be doing in the sun. Basically, the SPF is a measure of a sunscreen's ability to deflect harmful UVB rays, according to the American Academy of Dermatology. SPFs can range from 2 to more than 50. The higher the number, the greater protection the sunblock provides. The more fair your skin, the greater protection from the sun you will need. Also, the longer you will spend in the sun, the greater the SPF you should use.
Application
To optimize its effectiveness, sunblock should be applied 15 to 30 minutes before going out into the sun, according to the American Academy of Dermatology. Be sure to cover all areas of exposed skin, and don't forget the ears, hands and back of the neck. In general, you should use about 1 oz. of sunscreen in every application. That is enough to fill a shot glass, so keep that in mind as you are applying it. And remember that sunblock is only effective for about two hours and needs to be reapplied throughout the day. Also make sure to reapply after swimming or getting wet or sweating heavily.
Expiration
Food and Drug Administration regulation require all sunblock sold in the U.S. to remain effective for at least three years unless an expiration date is marked on the bottle. Keep this in mind when pulling out sunscreen from previous years. Always check to see whether its expiration date has passed. If so, toss it because it will not be effective.
Other Protections
Even when sunblock is used effectively, too much sun exposure is bad for your skin. In addition to applying sunscreen, there are other steps you can take to protect against sun damage. First, cover up when possible by wearing long-sleeved shirts and pants and wide-brimmed hats, the American Cancer Society advises. It's also best to try and avoid spending time in the sun when it is at its most intense, generally between 10 a.m. and 4 p.m. And remember that even on cloudy days, ultraviolet light filters through to ground level and can cause skin to burn.
Potential Hazards
Most sunscreens contain several active ingredients, but research on many of these ingredients is lacking. Much of the concern centers of nano-formulations of two ingredients in particular: titanium dioxide and zinc oxide. In nano-formulations, the particles have a diameter of less than 1 billionth of a meter. Research has demonstrated these small particles more efficiently block the sun's rays, the American Nutrition Association reports. However, some researchers believe not enough study has been done to determine definitively whether the use of these small particles can effect human health. In addition, the chemicals used in sunblocks could adversely affect aquatic ecosystems when it is washed off when people go swimming.
References
- American Cancer Society: How Do I Protect Myself from UV Rays?
- University of California, San Francisco School of Medicine Department of Dermatology: Sunblock
- American Academy of Dermatology: Sunscreens/Sunblocks
- American Academy of Dermatology: Facts About Sunscreens
- American Cancer Society: Skin Cancer Facts
