Tranexamic acid can treat ultraviolet radiation-induced pigmentation in guinea pigs.

Exposure of human skin to ultraviolet (UV) radiation causes erythema and pigmentation. Guinea pigs are recognized as having pigmentation similar to that of humans, after exposure to UV radiation. Recently, the curative effect of oral treatment of tranexamic acid in skin pigmentation was confirmed by many doctors in China. Our aim was to investigate the effects of tranexamic acid on pigmentation in the skin of guinea pigs exposed to UV irradiation and its possible mechanism. Guinea pigs were exposed to UVB radiation (60 min per day) for 30 days, skin pigmentation was clearly observed after that. 30 days later, tranexamic acid (5 mg/mL) was intradermally injected into the exposed regions every day after radiation to prevent or inhibit the pigmentation process. After 30 days the skin was removed and stained by HMB45 immunohistochemistry and the Masson Fontana-Ponceau method. HMB45 positive expression melanocytes in the basal layer of UV-exposed epidermis showed no significant differences in the regions to which tranexamic acid solutions had been applied compared with the control. But the melanin content was significantly reduced. We concluded that tranexamic acid has no effect on the number of melanocytes, it is likely that it affects the function of melanocytes, to inhibit the melanin expression in order to lighten moth patches.