It's All About Sunblock!

UV rays include UVA, UVB, and UVC rays. However, most of the time only UVA and UVB rays are harmful for our skin. Sun block usually has two measurements stating its power of sun protection - SPF and PA. SPF (sun protection factor) protects your skin against UVB rays. UVB rays have shorter wave lengths and are responsible for sun irritation, such as sun burns and peeling skin.

SPF on sun blocks indicates the extension of minutes a person can stay in the sun without burning. For example, an average person, can stay in the sun for 15 minutes without burning. So SPF 15 indicates that a person can stay in the sun 15*15 = 225 minutes without burning.

This measurement varies with individuals. If you can only stay in the sun for 10 minutes without burning, then a SPF15 sun block will only allow you to stay in the sun for 15*10 = 150 minutes without showing symptoms of sun burn and skin irritation.

SPF measurements also tell us about the percentage of UVB rays that we are shielded from. This percentage equals (SPF - 1)/(SPF). For example, for a SPF 15, the percentage of UVB rays that we are shielded from would be 14/15 = 93.33%. For a SPF to reach its maximum protection, each individual must make sure to apply about 2 milligrams of sun block per 1 cm^2 (centimeter squared) area of skin. Thus, the higher the SPF, the greater the coverage and protection. One important thing to note, however, is that although higher SPF offers higher and longer protection for our skin against harmful UVB rays, they also contain more chemicals which may be more stressful for our skin to handle. This in turn, may cause skin irritation and acne.

You may also notice the + signs following the SPF measurements. These are PA measurements which indicate the level of protection against UVA rays. UVA rays can harm your skin by causing wrinkles, loss of elasticity, skin aging, production of melanin by melanocyte (UVB rays also contribute to the increase of melanin production). PA measurements have 3 levels, +, ++, and +++.

PA + offers protection against UVA rays effectively for 2-4 hours, ++ offers effective protection for 2-8 hours, and +++ offers protection for more than 8 hours. Sometimes PA measurements are denoted by PPD. For example, PPD 12 offers 1.5 times stronger protection than PA +++.

For those of you who want to tan, you may notice that sunblock prevents the production of melanin, which is an indicator of skin color. More melanin means darker and tanner skin tones. This may cause you want to avoid wearing sun block at all cost. But keep in mind that over exposure to UVA rays and severe sun burn caused by UVB rays can lead to skin cancer, and often times the most severe type-melanoma

So keep in mind when choosing sun block the amount of hours you will be spending under the sun and look for the forecast that indicates the level of UV rays in your area to offer the best protection and least stress for your skin. A great model and map of areas with UV alerts is updated daily at http://www.epa.gov/sunwise/uvindex.html