It can activate tyrosinase, accelerate the production of melanin and tyrosinase, reduce the level of internal sulfhydryl groups, increase the content of copper ion and promote pigment synthesis.23 Our results show that after the treatment, the levels of VEGF were higher and the levels of ET-1 and MSH were lower in the study group compared to the control group (p<0.05), confirming the clinical value of PRP combined with TXA in the treatment of melasma. Here, EDN1 is linked to freckles.