According to The Ordinary, the formula boasts a technology called REDENSYL complex. Don’t let the obscure name put you off, though. Basically, it contains peptides (otherwise known as proteins) which are said to repair and strengthen hair. Alongside these peptides you’ll find caffeine, which the brand says makes the formula easily absorbed into the scalp, alongside castor oil, which has long been championed by trichologists and hair loss experts for stimulating hair growth and thickness when combined with regular scalp massage. There are also hair conditioners to increase softness and humectants (moisturising ingredients) like glycine.
Source: https://www.refinery29.com/en-gb/the-ordinary-multi-peptide-hair-density-serum-review