NL GHK Cu (TETRAPEPTIDE + CU) Synthagen Synthagen PL Selected Biomarkers Revealed Potential Skin Toxicity Caused by Certain Copper Compounds Scientific Reports PSA] Finally, a Dr. explains the mechanism behind the "copper uglies" : r SkincareAddiction If your GHK Cu or MOTS C injection leaves welts and burns like a hornet, it's usually not the peptide it's the technique. A few small tweaks can turn a sting into almost