Peptides sit in a messy middle: some have multi-study human data; others live on supplier decks and ex vivo histology.
A simple ladder for adjudication—Level A: independent RCTs on finished or close vehicles; Level B: supplier-sponsored clinicals with transparent methods; Level C: ex vivo / in vitro only; Level D: mechanism narrative with no skin outcome data.
Many “firming peptide” claims sit at B or C. That can still support careful cosmetic language (“helps improve the look of firmness”) if concentration and study duration are respected.
Catalog hygiene: store the peptide INCI, the evidence level, and the exact claim phrasing the study supports. Story peptides then stop contaminating stronger actives in the same SKU review.