By age 30, your skin produces about 25% less collagen. By 40, that number can reach 40%. This decline affects more than just how your skin looks. It changes how it heals, GHK Cu Dosage and Protocol: A Medical Provider's Guide to the 30 Day Cycle Perfect B PDF) The Human Tripeptide GHK Cu in Prevention of Oxidative Stress and Degenerative Conditions of Aging: Implications for Cognitive Health Supplementing With Zinc And Copper A Balancing Act Thorne Amazon.com: Skin Perfection Copper Peptide Serum GHK CU 1% for Face & Hair Copper Peptides for Skin, Hair, & Scalp 1% Blue Liquid for Face, Neck, Body, Scalp Multi Use Serum Booster with HealthyDerm Copper Peptides GHK Cu Beef Tallow for Skin: Blue Balm with Methy