Ingredient Guide

Hydrolyzed Keratin: A Conditioning Protein for Hair

Keratin is the protein hair is naturally made of, and in shampoos and conditioners it shows up as hydrolyzed keratin — broken into pieces small enough to cling to the strand. It works on the surface of the hair, smoothing the cuticle so hair feels softer, combs more easily, and looks fuller and stronger. That's a cosmetic effect you can feel and see, not a change to how hair grows.

  • Evidence-based
  • Structure/function only
  • No proprietary blends

What it is

Hydrolyzed keratin is keratin protein broken into smaller peptides so it dissolves into water-based formulas and binds to the hair fiber. The "hydrolyzed" part is what makes it useful: whole keratin would mostly sit on top, while the smaller fragments spread along the cuticle and settle into the more porous, worn spots where hair needs the most smoothing. It's a conditioning ingredient — it improves how hair behaves and looks.

How it works

On the hair, hydrolyzed keratin adsorbs to the outer surface and lays down a light protein film along the cuticle. That film smooths the strand so it reflects more light, feels softer, and slides past neighboring hairs with less friction — which is why hair tangles less and combs through more easily. By reinforcing the fiber surface, it can also cut down the small breakages that happen during brushing and styling. The effect builds with regular use.

Why the form & source matter

Hair-protein products come down to how the keratin is sized and delivered. Smaller peptides reach the more porous parts of the strand; slightly larger ones leave a smoothing film on the surface. A shampoo rinses quickly and deposits less; a conditioner has time to coat; a leave-in stays on to keep working through the day. Matching the format to the step is how you get smoother feel without weighing hair down.

How Monthlees uses it

Monthlees uses hydrolyzed keratin across a simple three-step routine: a Gentle Volume Shampoo to cleanse, a Gentle Volume Conditioner for slip and detangling, and a Leave-In Hair Mist that keeps a light conditioning layer on the hair between washes. Used together, they give hair a smoother surface, easier detangling, and a fuller, healthier-looking finish.

Frequently asked questions

What does hydrolyzed keratin do for hair?

It coats the strand and smooths the cuticle, so hair feels softer, combs more easily, and looks fuller and stronger.

Does keratin repair damaged hair?

It improves the look and feel of damaged hair by smoothing and reinforcing the fiber surface — a cosmetic conditioning effect rather than a biological repair.

What does "hydrolyzed" mean?

The keratin is broken into smaller peptides so it dissolves into the formula and binds to the hair instead of just sitting on top.

Shampoo, conditioner, or leave-in?

Each adds keratin at a different step — the shampoo cleanses, the conditioner detangles, and the leave-in keeps a light conditioning layer through the day.

Research & references

  1. Penetration of different molecular weight hydrolysed keratins into hair fibres and their effects on the physical properties of hair — International Journal of Cosmetic Science (2021) (source)
    Hydrolyzed keratin and hair-fiber cosmetic properties (surface conditioning).
  2. Exploring the Functional Properties of Hydrolyzed Keratin: Filling the Knowledge Gap on Surface Conditioning — ACS Omega (2025) (source)
    Functional properties of hydrolyzed keratin relevant to cosmetic hair applications.

References are provided for general educational context. They do not imply that this product treats, cures, or prevents any disease.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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Shampoo bottle with 'monthlees' branding and botanical design on a light gray background

Keratin Gentle Volume Shampoo

Ecocert COSMOS Natural volumizing shampoo — hydrolyzed keratin, caffeine, and rosemary cleanse and reactivate the scalp for extra body without weighing hair down.

Guest $31.95
Member
White bottle of 'monthlees' conditioner with a plant design on a light gray background

Keratin Gentle Volume Conditioner

Ecocert COSMOS Natural volumizing conditioner — hydrolyzed keratin, caffeine, and rosemary fortify strands while boosting body without heaviness.

Guest $31.95
Member
Keratin Leave-In Hair Mist

Keratin Leave-In Hair Mist

COSMOS Natural leave-in keratin mist — smooths frizz, adds shine, and softens hair without buildup or heaviness.

Guest $37.00
Member

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