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.