Purpose: To investigate the relation between pre-exposure skin pigmentation and the minimal melanogenesis dose (MMD)/minimal erythema dose (MED) ratio after a single narrowband ultraviolet B (nUVB) and solar simulator (Solar) exposure.
Background: In fair-skinned individuals, it is well known that the UV dose to give pigmentation (MMD) after a single exposure to UVB is larger than the UV dose to elicit erythema (MED) (MED<MMD), but it remains to be established if this is true also in dark-skinned individuals.
Methods: Eighty-four volunteers with a wide variation in skin pigmentation (Fitzpatrick skin types I–V) were included.
Results: After a single Solar or nUVB exposure we found that the ratio MMD/MED depends on skin pigmentation. In light-pigmented individuals, up to 1.9 MED is required to induce pigmentation (MMD). The MMD/MED ratio is about 1.5 in medium-pigmented and dark-pigmented individuals. In very brown-pigmented individuals the MMD/MED ratio is 1 (MED=MMD). This connection was most pronounced for facultative skin at wintertime. The ratio was almost stable for constitutive pigmentation with MMD/MED=1.3. The ratios were almost independent of skin type.
Conclusion: The ratio MMD/MED is highly dependent on skin pigmentation after a single exposure to Solar or nUVB and is independent of skin type.