Minimal erythema dose and minimal melanogenesis dose relate better to objectively measured skin type than to Fitzpatricks skin type

BACKGROUND: Fitzpatrick skin type (FST I-IV) is a subjective expression of ultraviolet (UV) sensitivity based on erythema and tanning reactivity after a single exposure. Pigment protection factor (PPF) is an objective measurement of skin sensitivity in all skin types after a single exposure. METHODS: The aim was to compare FST and PPF with clinically determined minimal erythema dose (MED) and minimal melanogenesis dose (MMD) in 84 persons with skin types I-V both after single and multiple exposures (one, four, five, six, or 12) to buttock and back skin. RESULTS: FST was better correlated to MED than to MMD, and FST correlated better to constitutive than to facultative pigmented areas after multiple exposures rather than to a single exposure. PPF was generally much better correlated to MED and MMD than FST especially after a single exposure and multiple exposures with steady-state pigmentation. Multiple regression analyses showed that MED was the only significant, or most important determinator, of both FST and PPF. The correlation coefficient was highly significant for PPF (r² =82). CONCLUSIONS: PPF is a better predictor of the individual UV sensitivity (linear relation) than FST (only 4 grades) and PPF can substitute FST.