Quantitative assessment of narrow-band UVB induced tanning during phototherapy in Korea

Abstract

Background/purpose: Narrow-band (TL-01) UVB lamps are being increasingly used for phototherapy of psoriasis and other dermatoses, for their excellent effect compared with broad-band UVB sources. Many patients receiving phototherapy have complained about the tanning effect of ultraviolet radiation especially in dark-skinned ones. So we wished to know the degree of pigmentation induced by phototherapy during narrow-band UVB treatment.

Methods: A total of 20 psoriasis patients receiving narrow-band UVB phototherapy were included in this study. A Minolta spectrophotometer CM-2002 was used to measure pigmentation. All patients were evaluated for skin color every seventh day for 7 weeks. The L* value (luminance) gives information about the relative lightness ranging from total black to pure white. The a* value represents the balance between red and green, and the b* value between yellow and blue.

Results: The L* values which indicate luminance decreased continuously until the 5th week, when maximum tanning was obtained. Afterwards minimal change was observed until the 7th week. The change of a* and b* values also showed the pattern that was compatible with the above results. The mean individual typology angle of our subjects was 41.9 degrees, which indicated they fell into "light" group of constitutional skin color category.

Conclusion: From this study, we found that pigmentation induced by narrow-band UVB phototherapy increased continuously until the 5th week and then did not progress. Our results provide standard data of skin pigmentation during narrow-band UVB phototherapy in Korean brown skin.