Cellular Glow Hair Serum 10% GHK Cu + 5% AHK Cu Peptides Some peptides are FDA approved drugs. Some are legal supplements. Some are neither. The same word, peptide, covers all three categories. The regulatory status of the specific compound is what determines legality. 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 GHK Cu Peptide for Hair Growth: Science, Benefits, and How It Works