Melasma is a hyperpigmentary disorder of the skin especially of the face. Compared with normal skin, histologic features of melasma include the enhanced activity of melanocytes, higher solar elastosis in upper dermis, basement membrane disruption which promotes melanocytes and melanin into the dermis, increased vascularization, and an increased number of mast cells. 1927nm fractional laser was approved to treat melasma with no major side effects, however,hyperpigmentation and recurrence occasionally happened after laser therapy. Mast cells may paly a key role in the refractory melasma and hyperpigmentation. We hypothesized that laser treatment may stimulate the activation of pre-existing mast cell in melasma skin and promote mast cell proliferation and degranulation to release mediators such as histamine (HA). HA has been demonstrated to increase the melanin content and tyrosinase activity of melanocytes and induce melanogenesis and morphological changes by activating cAMP-PKA pathway through H2 receptors on melanocytes5. H2R antagonist(H2RA) can suppress pigmentation by reducing the increase of activated melanocytes by UVB irradiation. In the present study, the investigators speculated that H2RA can enhance the efficacy of laser treatment of melasma and block the histamine-mediated melanogenesis and dendricity to prevent postoperative hyperpigmentation. The investigators combined 1927nm fractional laser with topical famotidine for melasma as a new therapeutic strategy to treat melasma.The investigators performed a split-face, single-blinded study to evaluate the efficacy and safety of 1927nm fractional laser with topical famotidine for the treatment of facial melasma.
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Modified Melasma Area Severity Score（mMASI）
Timeframe: week0，4，8，12，16