Light-induced skin cancer and prolonged uv-erythema.

The individual minimal erythema dose (MED) and the persistence of a marked erythema (8 MED) was monitored over 3 weeks (300 nm +/- 10 nm) in 4 groups: White students with fair complexion compared with students of homogenous pigmentation as well as skin carcinoma patients compared with a control group of the same age, i.e., older than 50 years. The MED of the 4 groups gives no significant differences, while the skin carcinoma group shows in 80% a prolonged erythema persistence (control group only 28%). This phenomenon does not seem to correlate with the skin type and may be useful in identifying high-risk patients prone to light-induced skin cancer.