This is a review paper that examines how copper levels affect cancer cells, not a study testing copper on human skin. Researchers found that copper can trigger a type of cancer cell death called cuproptosis, and that manipulating copper levels might help treat cancer—but this is theoretical science, not a proven beauty ingredient.

This wasn't an experiment; it's a literature review that summarized existing research on copper's role in cancer biology and potential therapeutic applications.

Funding not disclosed in abstract