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 Say hello to your skin's new BFF GHK Cu is a powerful peptide that supports collagen production, speeds healing, improves hair growth, and helps fight visible signs of aging. This tiny molecule Copper Peptides for Skin: What GHK Cu Does and How It Compares to Retinol GHK Cu Peptide The benefits, side effects, and more [2026] Biossance Squalane + Copper Peptide Rapid Plumping Serum