Dermalogica Invisible Physical Defense Mineral Sunscreen SPF30 is invisible, a weightless defense that blends easily on the skin, featuring only non-nano Zinc Oxide. Say goodbye to a thick, white residue with this physical SPF formula that provides added blue light protection and helps soothe away the effects of environmental aggressors. Bio-active Mushroom Complex helps soothe skin, and reduce UV-induced redness and dryness. Antioxidant Green Tea helps defend the skin against free radical damage. Ideal for all skin types, including sensitive ones. SPF is a measure of how much solar energy (UV radiation) is required to produce sunburn on protected skin (i.e., in the presence of sunscreen) relative to the amount of solar energy required to produce sunburn on unprotected skin.