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

BACKGROUND: Many reports have been released to assess skin types, skin colors and cutaneous sensitivity to broad band UVB or UVA. OBJECTIVE: This study was performed to investigate the usefulness of skin type and skin color as the parameter of narrow band UVB (NBUVB) sensitivity. METHODS: 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. RESULTS: 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. CONCLUSION: 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.