Assessment of the usefulness of skin phototype and skin color as the parameter of cutaneous narrow band UVB sensitivity in psoriasis patients

Many reports have been released to assess skin types, skin colors and cutaneous sensitivity to broad band UVB or UVA.This study was performed to investigate the usefulness of skin type and skin color as the parameter of narrow band UVB (NBUVB) sensitivity.The minimal erythema dose (MED) of 40 psoriasis patients was investigated by irradiating several doses ranging from 200 to 1500 mJ/cm2. Before phototesting, the skin color of buttock was measured with a tristimulus colorimeter.The median and mode value of MED of NBUVB was 950 mJ/cm2. Skin type was well correlated with the MED and there was a significant relationship between the L* value and MED, but not for the a* and b* values.The MED value of NBUVB in our study is a basic data to set the phototherapy protocol. Our result showed that skin type and L* value might be useful for predicting the sensitivity to NBUVB irradiation.