Topical or SubQ GHK Cu? Same molecule. Very different purposes. Topical you apply it on your skin. Think of it as feeding your skin from the outside. In a 12 week study of GHK Cu: The Peptide That Transforms Skin and Tissue Health Calibrate Hydration GHK Cu is one of the most talked about peptides in aesthetics right now. But how much of what you have heard about it is actually true? Copper peptide, known as GHK Cu, has Thermodynamically stable ionic liquid microemulsions pioneer pathways for topical delivery and peptide application ScienceDirect