A leave-in serum to check
The Ordinary Multi-Peptide Serum for Hair Density was listed at $24 for 60 mL ($0.40 per mL) on its US site on November 11, 2026. Its water-based formula lists Biotinoyl Tripeptide-1, Acetyl Tetrapeptide-3 and caffeine. The brand directs shoppers to use it as a leave-in on a clean, dry scalp.
Manufacturer · US offer, ingredients and directionsThe Ordinary Multi-Peptide Serum for Hair Density
What does “density” on the bottle tell you?
The manufacturer describes fuller-looking hair. The ingredient list confirms what is in the formula. It cannot show whether the finished serum changes hair count or which ingredient contributes to a visible change. FDA distinguishes cosmetic appearance claims from claims to restore hair growth.
US regulatorFDA · Cosmetic and drug claims
Choose by the step you want
If your priority is lift while styling, start with a product designed for volume at the roots. If you are comparing leave-in scalp serums, check where each one goes, how often the label calls for use and the cost per mL before adding a daily step.