SPF is an acronym for ‘Sun Protection Factor,’ a number assigned to a product to measure the length of time it can, in theory, protect skin from reddening from UVB, compared to how long the skin takes to minimally redden without the protection of that product. The protected time can be determined by taking the usual time the person reddens while unprotected, times the SPF number of the product. For example, if it takes this person 20 minutes to redden usually, the product assigned an SPF 15 will in theory protect this person 20 x 15, or 300 minutes, approximately 5 hours. Reapplication ahead of this 5 hour mark will help, though. Don’t wait until the last minute to reapply! The most effective tool you can use in the war against skin aging and cancer is education on the use of SPF. While the SPF has become the standard measure for UVB protection, none exists for UVA.
What is SPF?
