Ultraviolet Rays, UVA vs. UVB
As many of us are now experiencing the winter weather (albeit global warming winter), it is still important to wear sunscreen each day. Why you ask? Well here is a brief synopsis of the difference between UVA and UVB rays, and how they are present year-round!
Ultra-Violet A Radiation (UVA)
UVA rays emitted by the sun are the deepest penetrating UV radiation. UVA rays cause wrinkles and premature aging in the skin. Additionally, the effects of UVA rays are cumulative, and may contribute to DNA damage as well as skin cancer. UVA light can penetrate windows and, due to its longer wavelength, filters deeper into the skin than UVB light. Most sunscreens contain an SPF to protect against UVB rays. Subsequently, it is important to use one with a “broad spectrum” to protect the skin from UVA rays as well. Since UVA rays do not cause sunburn, they cannot be measured with an SPF. Ingredients approved by the FDA to protect the skin from UVA rays include Parsol 1789 (Avobenzone), Titanium Dioxide, Zinc Oxide, Oxybenzone, and, most recently, Mexoryl. UVA rays are the same strength year-round, regardless of the season.
Ultra-Violet B Radiation (UVB)
UVB rays emitted by the sun cause sunburns and are responsible for causing skin cancer. UVB rays have shorter wavelengths than UVA rays, and affect the upper layer of the skin. The body produces Melanin to protect skin cells from UVB rays, and overexposure results in sunburn. Sunscreens provide an “SPF Rating” that describes the amount of protection provided against UVB exposure. The higher the SPF number, the longer you can be in the sun without burning. For example, if you burn after 15 minutes, an SPF of 15 will allow you to remain in the sun 15 times longer without burning (the equivalent of 225 minutes). An SPF of 15 will block approximately 93% of the sun’s rays while an SPF of 45 will block approximately 98%. However, the percent of the sun’s rays blocked does not increase incrementally, and above SPF 30 there is only a small difference in percentages. UVB rays are strongest during the summer months when the earth is closer to the sun.
Thanks for explaining UVA/UVB Ultraviolet Rays. I never could figure out what the difference was. I plan to use sunscreen all year round as you at MBB suggest. I will also look for a product hat contains ingredients that are most benefical to the skin. Thanks once again. A girl cannot do enough to ‘hold back the hands of time.” Love the site. Lilly.
posted on January 14, 2008 at 2:48 pm