Comparison of Minimal Erythema Dose Between Affected and Unaffected Skin in Vitiligo Patients With Fitzpatrick Skin Phototypes III, IV, and V

ABSTRACT Introduction Vitiligo is a depigmenting autoimmune disease. This study aimed to determine the minimal erythema dose (MED) of vitiligo‐affected skin and normal skin among patients with skin phototype III, IV, and V. Methods A cross‐sectional study was performed. MED was determined using a handheld device with wavelength of 311 nm. Vitiligo severity was measured using the Vitiligo Area Scoring Index (VASI) while disease activity was assessed by the Vitiligo Disease Activity (VIDA). Sun exposure was quantified by the Sun Exposure Index (SEI). Results A total of 36 patients (mean age of 49.06 ± 21.29 years old) participated with 12 patients from each skin phototype. MEDs of skin affected by vitiligo were 255 ± 120.3, 280 ± 93.4, and 525 ± 226.1 mJ/cm 2 for phototypes III, IV, and V respectively. The MEDs of unaffected skin were 465 ± 120.3, 580 ± 123.6, and 1150 ± 116.8 mJ/cm 2 for phototypes III, IV, and V respectively. The MEDs for skin affected by vitiligo were 45%, 52%, and 54% less than the MEDs of unaffected skin for phototypes III, IV, and V respectively. The differences in MEDs between vitiligo‐affected skin and unaffected skin were significant for all skin phototypes ( p < 0.001). MED of skin with vitiligo negatively correlated with vitiligo severity, r = −0.426, p = 0.01. There were no significant correlations between MED and VIDA, disease duration, or SEI. Conclusion MED of skin with vitiligo was much lower than unaffected skin, and MEDs between skin phototypes III, IV, and V differed despite similar depigmentation. MED was not influenced by vitiligo disease activity, duration, or sun exposure.