Time course of ultraviolet-induced skin reactions evaluated by two different reflectance spectrophotometers: DermaSpectrophotometer® and Minolta spectrophotometer CM-2002®
Many attempts have been made to quantify ultraviolet (UV)-induced erythema and pigmentation, but most studies have been focused on the initial changes of reaction for a few hours or days and neglected the later events. Methods:
A time course of skin colour changes induced by fluorescent sunlamp with a broad band of UVA and UVB radiation was evaluated in 15 Korean male volunteers using two different reflectance spectrophotometers for 28 days. The results were presented by E (erythema)- and M (melanin)-index as well as values converted to the L*a*b* system recommended by the CIE (Commission Internationale de l'Eclairage). Results:
The mean individual typology angle of the subjects was 46.6°, which indicated ‘light’ group in constitutional skin colour category. A day after UV exposure, the L* and b* values decreased significantly, following the colour direction of persistent pigment darkening. The values went in the opposite direction persistently until after the 1st week, when maximum tanning was obtained. They then shifted toward their original positions, parallel to the constitutive melanization axis. The a* index showed a significant increase toward the mean colour of haemoglobin on day 1. It returned to its original value along the constitutive melanization axis. The E-index showed a maximum value at day 1, then returned to baseline. The value of M-index reached a peak at day 7. There was no significant difference between the two instruments, but each has its own characteristic features. Conclusion:
These promising quantitative methods should enable us to achieve objective measurement of the dermatophysiologic changes and to evaluate the efficacy of therapeutic modalities on skin disorders without the inherent errors associated with subjective judgement. Our results provide standard data on a time course of UV-induced skin erythema and pigmentation.
Document Type: Research Article
Affiliations: Department of Dermatology, Seoul National University College of Medicine and Clinical Research Institute, Seoul National University Hospital, Seoul, South Korea
Publication date: 2002-02-01