Alternating tretinoin and GHK Cu (copper peptides) nightly maximizes anti aging benefits while minimizing irritation. , Both are potent but DIFFERENT actives. Tretinoin speeds up cell turnover and Copper Peptides vs Retinol: Do You Need Both? Nubeean Noosa GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? GHK Cu Copper Peptide Face Tonic for Firmer Looking Skin Copper Peptides vs Retinol Can You Use Copper Peptides With Retinol? Ghk Cu Vs Tretinoin For Anti Aging