Central nervous system uptake of intranasal glutathione in Parkinson's disease npj Parkinson's Disease GHK Cu Copper Peptide Injections: Advanced Skin Rejuvenation Glutathione Getting the k'NAC'k of Parkinson's disease The Science of Parkinson's A GHK Cu face serum appears blue because the active ingredient, GHK Cu (copper peptide), is naturally a blue colored powder, meaning its inherent color transfers to the serum when mixed in; this blue hue