Copper compounds are also used as actives or excipients in cosmetic and pharmaceutical products, e.g., copper peptide for skin regeneration purposes, cupric aspirinate and cupric salicylate for rheumatoid arthritis treatment, copper conjugated dendrimer for anti-tumoral activity, and copper liposome for enhanced stability of doxorubicin 5,6,7,8,9
The standard advice is to use vitamin C in the morning and copper peptides in the evening, then alternate copper peptides with retinol on different nights, or use them in the same evening routine with copper peptides applied first
In instance, selenium is necessary for glutathione enzyme activation
Here, those three amino acids form glutathione in a complex biochemical process
If you wanna become a real HA-and-the-skin expert you can read way more about the topic at hyaluronic acid (including penetration-questions, differences between high and low molecular weight versions and a bunch of references to scientific literature)
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