What does “spf” mean?

SPF = Sun Protection Factor, which define the protection against UVB rays. It is based on a scientific method that calculates the ratio between the time required to get a sunburn and the application of the product. Both SPF30 and SPF50 sun care products protect the skin, the difference is that SPF30 blocks about 97% of UVB rays, SPF50 blocks about 98%. In Europe, sunscreen with an SPF superior to 50 is called “SPF50+” while in other regions SPF70,80,100...can be found. A SPF100 blocks around 99% of UVB rays.