Background: Melasma is characterized by increased pigmentation and photodamaged skin. These features suggest that melasma patients might have a significant impact on cutaneous biophysical characteristics.
Objective: The cutaneous biophysical characteristics in melasma were investigated.
Methods: A total of 16 Korean volunteers with melasma were enrolled. The melanin index/erythema index, stratum corneum (SC) hydration, sebum content, and transepidermal water loss (TEWL) were measured and compared between lesional and perilesional normal skin. The TEWL was re-measured immediately and 5 hours after tape stripping to investigate SC integrity and barrier recovery rate. The sebum content was measured at 30 minutes and 5 hours after degreasing by facial washing to estimate the sebum excretion rate. Skin biopsy was performed in 11 volunteers to measure the SC thickness and to study the expression of lipid metabolism associated genes such as peroxisome proliferator-activated receptor alpha (PPAR-α), and arachidonate 15-lipoxygenase, type B (ALOX15B).
Results: The melanin index, erythema index, and SC hydration were significantly higher in lesional skin compared to nonlesional skin, whereas the measurement of basal TEWL showed no significant difference. However, the increased rate of TEWL after tape-stripping was significant higher in lesional skin compared to nonlesional skin. Also, barrier recovery rate of lesional skin was significant delayed. The melanin index was found to be inversely correlated with the barrier recovery rate. There was no significant difference between the basal sebum content and the sebum excretion rate. The expression between PPAR-α and ALOX15B was not significantly different, whereas SC thickness was reduced in lesional skin, which showed correlation with the barrier recovery rate.
Conclusions: Melasma skin showed a normal hydration state and sebaceous gland activity. However, the SC integrity and barrier function were impaired in lesional skin of melasma. The SC thickness was reduced in lesional skin, and it positively correlated with the barrier recovery rate. These results suggest that improving SC function should be considered in treating melasma.