Hydrolyzed Keratin: Does It Actually Repair Your Hair?
INCI: Hydrolyzed Keratin · also listed as Keratin peptides, Hydrolysed keratinYour hair is roughly 90% keratin, so putting keratin back sounds obvious. The failure mode - protein overload - is one of the most common self-inflicted hair problems there is.
Effective on damaged hair, and easy to overdo
Keratin broken into fragments small enough to be useful. They settle into eroded gaps in a damaged cuticle and cortex as a temporary patch: measurably more strength, less porosity, better heat tolerance. On bleached hair the difference is obvious.
What it does not do is rebuild. The patch is deposited, not bonded into the original keratin structure, and it washes out over a few washes. Because protein is stiff, applying it too often produces the opposite of what you wanted - rough, straw-like hair that snaps more easily. Frequency, not safety, is the thing to get right.
- INCI name
- Hydrolyzed Keratin
- Also on labels
- Keratin amino acids, hydrolyzed wheat / soy / silk / rice protein. Different sources, same mechanism — they differ mainly in fragment size and how heavy they feel.
- Job in hair care
- Substantive protein. The peptide fragments bind to negatively charged damaged sites on the shaft, filling cortical voids and smoothing lifted cuticle scales.
- Found in
- Bond and repair masks, protein treatments, post-bleach conditioners, heat protectants, salon smoothing aftercare.
- Typical level
- 1–3% in a treatment mask; much lower in a shampoo, where contact time is too short to matter.
- Regulatory status
- Permitted worldwide, unrestricted. Note that a salon "keratin treatment" usually means a formaldehyde-based smoothing service — a completely different process.
- Hairmony class
- ActiveScored by the Hairmony engine, so it actually moves which products you get recommended.
- Scored for
- +damaged hair+heat protection+porosity control−fine hair (at high frequency)A high-potency damaged-hair active, dialled down for fine, low-porosity hair where protein builds up fastest.
What it does to hair and scalp
Whole keratin applied to hair would do nothing — too big to penetrate. Hydrolysis chops it into short peptides small enough to enter the shaft, carrying charges that make them stick rather than rinse off.
Damaged hair is eroded, and erosion leaves it more negatively charged, so the peptides deposit where the damage is rather than uniformly. Strength rises and porosity drops. But they are held by charge attraction, not the disulfide bonds that give hair its structure — so three to five washes later, most of it is gone.
Worth using if
- Your hair is bleached, highlighted, relaxed or permed
- Wet hair stretches a long way then snaps
- Your hair is high-porosity, or feels mushy when wet
Go easy if
- Your hair is fine and low-porosity
- It already feels rough, brittle or straw-like
- Several products in your routine contain protein
Protein overload: the failure mode
Protein makes hair stronger, and stronger is not better. Hair needs to bend without breaking. Protein raises strength and lowers elasticity, and past a point hair becomes rigid. Rigid hair snaps — and the symptoms look exactly like the damage people are treating, so they use more.
The stretch test settles it. Pull a wet strand gently. Stretches a long way, or feels mushy: it wants protein. Barely stretches and snaps at once: it has too much and wants moisture. Overload is fixed with a few weeks of moisture-focused conditioning and a clarifying wash.
In practice: start at once every two weeks for damaged hair, once a month for healthy hair, always follow with a moisturising conditioner, and count all your protein sources — not just the mask.
Not medical advice. This page describes how an ingredient behaves on hair and scalp. If you have a persistent rash, sores, sudden shedding or a diagnosed scalp condition, see a dermatologist before changing anything.
Frequently asked
Does hydrolyzed keratin actually repair damaged hair?
It patches rather than repairs. The fragments fill eroded gaps in the cuticle and cortex, measurably increasing strength and reducing porosity while present. They are held by charge attraction rather than bonded into the hair, so the effect fades over three to five washes.
How do I know if I have protein overload?
Wet a strand and pull gently. Hair with too much protein barely stretches and snaps at once, and feels rough even straight after conditioning. Hair that needs protein stretches a long way and feels mushy. Overload is treated with moisture and a clarifying wash.
Is a salon keratin treatment the same as keratin in my conditioner?
No. A salon keratin or Brazilian blowout is a formaldehyde-based smoothing service that chemically restructures the hair and carries an inhalation risk regulators are examining. Hydrolysed keratin in a bottle is a temporary conditioning protein. Only the word is shared.
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