It helps brighten skin and improve overall tone
The review article referenced findings that GHK-Cu modulates thousands of human genes involved in healing and inflammation, tissue remodeling, and antioxidant responses
Cacciatore, I., Cornacchia, C., Pinnen, F., Mollica, A., & Di Stefano, A
The larger needle itself may be more painful to use especially if it's a much larger gauge and you will need finer control to make sure you don't inject too quickly and cause further pain
doi: 10.3389/fimmu.2021.708101 230 RobbianiD
Cyanocobalamin vitamin B12 used for vitamin B12 deficiency