The relationship of sun protection factor to minimal erythema dose, Japanese skin type, and skin color.

The relationship of sun protection factor (SPF) to minimal erythema dose (MED), Japanese skin type, and skin color was investigated on the unexposed backs of 48 healthy subjects. SPF of a UVB-sunscreen was determined using sun lamps as a light source. A significant correlation was found between SPF and MED; subjects with lower MED showed higher SPF. The average SPF decreased with increasing skin type. There was no significant correlation between SPF and skin color (L*a*b* color system).