This is because melanin production resumes once glutathione levels drop in the body
10.3390/agriculture13040789 68 NishikimiM.RaoN
What to look for in a vitamin C serum Form: L-ascorbic acid Concentration: 10% to 20% Ingredient combo: L-ascorbic acid, tocopherol (vitamin E) or glutathione, ferulic acid Packaging: dark or tinted glass bottles with airless delivery Price: not a factor in quality, but opt for the brand that fits your budget Form Vitamin C can appear on the ingredients label under several different names, but the one you want is L-ascorbic acid, which is the most studied and effective
Science of the Total Environment, 901 , Article 165922
In order to lighten darkened skin or melasma, I recommend a course of Glutathione and vitamin C intravenous drips until the skin or pigmentation lightens then a reducing dose regularly will maintain your lovely clear even tone skin
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