UVA/UVB, SPF, Sunscreen/SunBlock: What Does It All Mean?

As our consciousness about the sun's effect on our skin is being raised, we are paying more attention to products that will offer the best measure of protection. The number of products, claims, and technical jargon leave many uncertain about what constitutes the appropriate protection.

I hope to offer some fundamental understanding, which may assist in the right option for you. Ultimately, it is important to note that information is not static and is ever changing. Your doctor or dermatologist is your best consultant in this matter.

UVA: are ultraviolet long-wave solar rays that penetrate the skin more deeply and are considered the main cause of wrinkling and, studies suggest, skin related cancers.

UVB: are ultraviolet short-wave solar rays that are more potent in producing sunburn and give rise to melanoma.

Sunscreen: chemically absorbs UV rays.

Sunblock: physically deflects UV rays.

SPF: stands for "sun protection factor" against skin reddening from UVB - it does not apply to UVA protection. The time it takes for the skin to begin to redden will differ between persons, as many factors can affect the rate. Assuming that you begin to redden after 30 minutes then a SPF15 sunscreen will offer 15 times the 30 minutes of protection, or 7.5 hours of protection.

SPF15 blocks 93% of UVB
SPF 30 blocks 97% of UVB
SPF 45 blocks 98 % of UVB

As the degree of protection is marginal after SPF15, it is the recommended minimum level. Regardless, the Skin Cancer Foundation recommends reapplication every 2 hours and after swimming.

Broad Spectrum Protection: the phrase may have a different regional or international application. It is best to check with a pharmacist to see if it is present in the sunscreen or sunblock you are purchasing. If it is present, SPF15 will do a good job against UVB and short UVA rays; if it also contains avobenzone, zinc oxide, or titanium dioxide, it should be effective against the entire UVA spectrum.

What is the best protection?
Avoid the sun between 10 am and 4 pm, use sunscreen, sun protective clothing, sunglasses, and sit in the shade.