Phenotypic characters related to skin type and minimal erythemal dose.

Minimal erythemal dose (MED) was determined in 155 healthy Caucasoid subjects. Hair color, eye color, number of freckles, and history of sun reactivity and tanning ability, according to the system proposed by Fitzpatrick, were also recorded. In the subjects with skin type I, the values of MED were relatively homogeneous, whereas in subjects with skin types II, III and IV there was a wide variation of MED values. In spite of this variation, a good correlation was found between MED and skin types. MED was found to correlate with hair color, eye color and number of freckles only for some variants of these characters. Low values of MED correlated significantly with red hair, blue eyes and highly freckled skin. Between other variants of the same characters, MED values did not differ significantly. This means that phenotypic characters suggest low MED values only in individuals with red hair, blue eyes and many freckles. In these subjects the phenotypic characters studied may be considered indicative of cancer risk. For all other Caucasoid people the phenotypic characters studied are not predictive of MED nor, probably, of cancer risk.