To investigate the evaluation index of melasma staging by clinical manifestations and non-invasive skin detection technology.

A total of 195 patients with a clinical diagnosis of melasma were enrolled from the First Affiliated Hospital of Kunming Medical University. The skin with lesion enlarged, color darker, erythema, red occured after scratching or lesion faded after compressing with glass belonged to the active stage; on the contrary, it was in the stable stage. Reflectance confocal microscopy (RCM), dermoscopy, Mexameter 18 and LAB were used to observe skin lesions of different stage of melasma.

There were 115 patients (59.0 %) in the active stage of melasma and 80 patients (41.0 %) in the stable stage. DMA score in active stage 35.08±10.59 were significantly higher than that of the stable stage 15.06±9.20 (P<0.05). There were statistically significant difference in the quantity of inflammatory cell and blood vessels between two stages of melasma (P<0.05). Erythema index (EI) in active stage of melasma 376.35±61.39 were higher than that of the stable stage 320.36± 62.40 (P<0.05). A-value in active stage of melasma 13.28±1.75 were higher than that of the stable stage 12.34± 1.78 (P<0.05). However, there were no siginificant differences in the quantity of melenin, melanin index (MI) , L-value and B-value.

Melasma could be divided into active stage or stable stage, respectively, according to its clinical manifestations. DMA score, quantity of inflammatory cells and blood vessels, EI and A-value could be used as the reference index of melasma staging.

Melasma; Clinical stage; Non-invasive skin detection technology; Dendritic melanocyte activity; Erythema index