SPF measures sunscreen protection from UVB rays, the kind that cause sunburn and contribute to skin cancer.SPF does not measure how well a sunscreen will protect from UVA rays, which are also damaging and dangerous. Dermatologists recommend using a SPF15 or SPF30 sunscreen. Higher SPFs don’t give much more protection. SPF, or Sun Protection Factor, is a measure of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn, damages skin, and can contribute to skin cancer.
Sunscreens with really high SPFs, such as SPF 75 or SPF 100, do not offer significantly greater protection than SPF 30 and mislead people into thinking they have more protection than they actually do. Additionally, in order to have broad spectrum protection, the UVA protection should be at least 1/3 of the UVB protection. High SPF sunscreens usually offer far greater UVB than UVA protection, thus offering a false sense of full protection.