sun protection factor
factor describing the protective quality of a sunscreen against solar ultraviolet radiation, normally determined by in vivo testing
Note 1 to entry: The sun protection factor is usually determined by comparing the dose of ultraviolet radiation from a solar simulator (often a xenon lamp) required to produce just-perceptible actinic erythema approximately 24 h after exposure in ultraviolet-irradiated human volunteers, with and without a standard amount of the sunscreen being present (
Note 2 to entry: The sun protection factor can also be determined by equivalent in vitro methods.
Note 3 to entry: The sun protection factor has unit one.
Note 4 to entry: This entry was numbered 17-1278 and 17-1243 in CIE S 017:2011.