The Sun Protection Factor (SPF) is a numerical rating displayed on sunscreen packages. The higher the number the better protection against Hazardous effects of UVB rays. SPF does not relate in any way to a product's ability to protect you against UVA rays.

At present, there is no standardized system for measuring UVA protection. A higher SPF number does not protect you against burns from UVA rays, aging, wrinkling, and other long term skin injuries that can lead to melanoma and skin cancer-unless the product also contains the active ingredients that are proven to protect against UVA, too-Avobenzone (Parsol 1789®), titanium dioxide or zinc oxide.

SPF 15 is generally considered to be adequate for higher UV zones however a higher protection factor such as SPF 30 gives better protection in zones where the sun is stronger such as south Africa and Australia.

Sun block is not only for summer use --on a beach day. Bright sunlight reflects off snow in winter also calls for a good sun protection cream.

SPF is calculated by comparing the amount of time needed to produce a sunburn on protected skin to the amount of time needed to produce a sunburn on unprotected skin.

A product is rated SPF 2 if a person who normally starts to burn after 10 minutes without sun protection begins to burn after 20 minutes with the sun protection product. (20:10 = 2). An SPF of 30 means that it takes a person 30 times longer to burn from UVB overexposure when using that product than if he uses nothing at all.