PROTEIN
Hydrolyzed Keratin
- protein
Fragments of the same protein hair is made of. They fill gaps on damaged strands and make hair feel firmer for a few washes.
- products in our library
- 145
- of researched products
- 4%
- on the label, in our conditioners
- usually #10
- most common in
- Conditioner
- in water
- Water-soluble
At a glance
Four named levels, read from this ingredient’s chemical class, its charge, its solubility, or where it sits on the labels we have. More dots means more of the property named — never “better”.
How much of it is left on hair between washes.
What it takes to get it off the hair again.
Smaller fragments travel further into the strand.
Read from where it sits on the labels we have, not from the molecule.
| Property | Level | Out of |
|---|---|---|
| Buildup risk | Low | 1 of 5 |
| Rinse-out behaviour | Rinses clean | 5 of 5 |
| Fragment size | Small | 2 of 5 |
| Stiffening potential | Slight | 2 of 5 |
What it does for a formula
What Hydrolyzed Keratin does
The general function first, then how the role changes by product type where we have researched it.
Sticks to damaged areas of the surface and temporarily firms them.
Welcome on limp or damaged hair, unwelcome on hair that already feels rigid.
Fragments small enough to attach to worn areas of the strand — the protein that works.
The film is what holds a shape once the water has gone.
Charge
Charge is not recorded for this ingredient.
Solubility
Rinses out with water alone — it does not accumulate on hair between washes.
Where it appears
Where it appears
One row per product category in our library: how many products list it, what share of that category that is, and where it typically sits on the label.
| Product type | How common | Typical position on label ? |
|---|---|---|
Conditioner
32 products
|
secondary · #10 | |
Shampoo
30 products
|
secondary · #11 | |
Mask / treatment
26 products
|
secondary · #18 | |
Leave-in
22 products
|
secondary · #13 | |
Styler: mousse
6 products
|
secondary · #13 | |
Co-wash
5 products
|
secondary · #20 | |
Finisher: oil
4 products
|
secondary · #16 | |
Heat protectant
4 products
|
supporting · #6 | |
Styler: gel
3 products
|
secondary · #9 | |
Styler: paste
3 products
|
secondary · #28 |
7 more product types
| Product type | How common | Typical position on label ? |
|---|---|---|
Finisher: anti frizz finish
2 products
|
secondary · #13 | |
Finisher: serum
2 products
|
secondary · #9 | |
Styler: volumizer
2 products
|
secondary · #25 | |
Finisher: shine spray
1 product
|
secondary · #10 | |
Styler: hairspray
1 product
|
secondary · #9 | |
Styler: smoothing cream
1 product
|
secondary · #35 | |
Styler: texture spray
1 product
|
supporting · #8 |
| Product type | Products | Share of category | Median position | Earliest position | Band |
|---|---|---|---|---|---|
| Conditioner | 32 | 5% | 10 | 5 | secondary |
| Shampoo | 30 | 4% | 11 | 6 | secondary |
| Mask / treatment | 26 | 7% | 18 | 8 | secondary |
| Leave-in | 22 | 5% | 13 | 3 | secondary |
| Styler: mousse | 6 | 4% | 13 | 6 | secondary |
| Co-wash | 5 | 5% | 20 | 8 | secondary |
| Finisher: oil | 4 | 2% | 16 | 11 | secondary |
| Heat protectant | 4 | 3% | 6 | 5 | supporting |
| Styler: gel | 3 | 2% | 9 | 9 | secondary |
| Styler: paste | 3 | 3% | 28 | 13 | secondary |
| Finisher: anti frizz finish | 2 | 9% | 13 | 8 | secondary |
| Finisher: serum | 2 | 3% | 9 | 9 | secondary |
| Styler: volumizer | 2 | 3% | 25 | 10 | secondary |
| Finisher: shine spray | 1 | 2% | 10 | 10 | secondary |
| Styler: hairspray | 1 | 1% | 9 | 9 | secondary |
| Styler: smoothing cream | 1 | 2% | 35 | 35 | secondary |
| Styler: texture spray | 1 | 2% | 8 | 8 | supporting |
No product-type differences have been researched yet — the reading below is computed from where it sits on the labels in our library.
Position footprint
Every listing in our library, by position on the label.
| Positions | Zone | Listings |
|---|---|---|
| 1-3 | Leading | 1 |
| 4-8 | Supporting | 28 |
| 9-15 | Secondary | 70 |
| 16-25 | Lower | 44 |
| 26+ | Trace | 24 |
How to read this
US labelling rules put ingredients above 1% in descending order of amount; below 1% they may be listed in any order.
So position tells you about relative amount only above that line, and we never convert a position into a percentage.
Who should pay attention
Conditional formulation guidance, scoped to a hair condition and to the positions where it is meaningful. It is not a conclusion about any finished product, and not a conclusion about you.
Filling surface gaps evens out the cuticle, which is part of what makes damaged hair comb and reflect light more like undamaged hair.
Film formers are what hold a style: they dry into a connected film across the strands so the shape resists movement.
Size decides where it goes. In fibre testing, fractions around 221 and 2,577 Da reached the cortex while a 75,440 Da fraction stayed on the surface. A label prints the name, never the size, so a protein line is a claim about the ingredient rather than about the depth.
Read where it is listed in the first three ingredients, positions 4–8 or the lower half of the ordered list.How rigid the finish is depends on which polymer it is and what the formula pairs with it, not on there being one.
The stiffening is measurable, not imagined: the mid- and high-molecular-weight fractions raised the fibre's Young's modulus at both low and high humidity. That is the rigidity protein-reactive hair is reacting to, and it washes out rather than accumulating.
Read where it is listed in the first three ingredients or positions 4–8.Rows marked “researched” were read for this ingredient and cited below; the rest are read from its chemical class.
Why it matters to shoppers
What this ingredient is evidence of, what it is not evidence of, and what our own method can and cannot tell you.
- temporary strength on damaged hair
- a protein that binds to damaged hair
- a style that holds
- a rinse-clean feel
- an exact safety score — we do not publish one, for any ingredient
- how a finished product performs by itself — that is the whole formula, not one line of it
- the exact percentage in a bottle — label position never converts into a number
- a secondary protein, listed below the main ingredients in our conditioners
- it was on the label of every product we counted — we read printed ingredient lists, not marketing copy
- that it repairs hair permanently
- stiffness — only how much of it there is does that
- that a product is right or wrong for you
We do not publish safety scores or hazard grades. Where a regulator has published a restriction or a use condition, we state it and cite it; otherwise we describe what the ingredient does and stop.
Commonly paired with
Ingredients that appear alongside this one most often in our library. Near-universal ingredients are excluded — they pair with everything and tell you nothing.
- Disodium EDTA · 62
- Cetrimonium Chloride · 60
- Hexyl Cinnamal · 54
- Behentrimonium Chloride · 48
- Amodimethicone · 46
- Dimethicone · 42
- Benzyl Alcohol · 42
- Tocopheryl Acetate · 40
- Propylene Glycol · 40
- Sodium Chloride · 37
The number beside a name is how many products in our library list both.
These ingredients tend to appear together to keep the formula stable, improve feel after rinsing, and give it a scent.
Found in these products
The most prominent placements first. The badge is the position on that product’s own ingredient list.
CHI · Leave-in
Infra Keratin Mist
#3 on the label · $1.67/oz
Hask · Leave-in
Keratin Protein 5-in-1 Leave in Spray
#4 on the label · $1.17/oz
OGX · Shampoo
Blonde Enhance + Purple Toning Shampoo
#4 on the label · $0.82/oz
Ouai · Conditioner
Medium Hair Conditioner
#5 on the label · $3.20/oz
Pantene · Heat protectant
Keratin Leave-In Repair Treatment
#5 on the label · $1.84/oz
Pantene · Heat protectant
Miracle Rescue 10-in-1 Multitasking Spray + Keratin
#5 on the label · $2.27/oz
Joico · Finisher
K-PAK Color Therapy Luster Lock Glossing Oil
#6 on the label · $11.46/oz
Not Your Mother's · Leave-in
Way To Grow Leave-In Conditioner
#6 on the label · $1.46/oz
OGX · Shampoo
Anti-Breakage + Keratin Oil Shampoo
#6 on the label · $1.38/oz
SoCozy · Styler
Kids Sensitive Hair Style Foam
#6 on the label · $1.67/oz
TRESemme · Heat protectant
Heat Protect Spray for 5-in-1 Anti-Frizz Control Keratin Smooth with Marula Oil
#6 on the label · $1.00/oz
Nexxus · Conditioner
Nexxus Humectress Ultimate Moisture Conditioner
#7 on the label · $1.48/oz
See all 145 products in the library that list Hydrolyzed Keratin
Identity
What this entry is, and what our references call it.
No public-domain structure depiction is available for this entry.
Hydrolyzed Keratin
- film former
- hydrolysed protein
- hydrolyzed keratin
- hydrolyzed keratin (and) water
For your hair?
Whether Hydrolyzed Keratin matters for your hair depends on your hair.
the 6th most-listed protein or amino acid in our libraryWhat this ingredient does, and where it sits on the labels we have researched.
A verdict on any product that contains it, and never a safety grade.
We do not physically test your hair. Everything above is read from the ingredient lists in our library and from published references — the consultation is what turns it into a plan.
References
Sourced Backed by a manufacturer or regulatory source.
This ingredient
- Manufacturer or regulatory International Journal of Cosmetic Science — Malinauskyte et al. (2020), TRI Princeton. Tested hydrolysed keratins at 221 Da, 2,577 Da and 75,440 Da: the low and mid fractions penetrated deep into the cortex while the high fraction adsorbed onto the surface; the mid and high fractions increased the fibre's Young's modulus at both 20% and 80% relative humidity. · accessed 2026-08-30
How this page was made
- Every number above is counted from the ingredient lists in our own product library — 145 of 3889 researched products list this ingredient. Nothing on this page is written per ingredient.
- The dots are named levels read from an ingredient’s chemical class, charge, solubility, or where it sits on the labels we have — never a score.
- US labelling rules put ingredients above 1% in descending order of amount; below 1% they may be listed in any order. Position tells you about relative amount only above that line, and we never convert a position into a percentage.
- The prominence bands (leading, supporting, secondary) are the same ones the product pages use to read a single label, applied here to the median position across a category.
- We do not publish safety scores or hazard grades. Where a regulator has published a restriction or a use condition, we state it and cite it; otherwise we describe what the ingredient does and stop.
- Identifiers and references appear only when a published source is attached to this entry; where none is, the row is simply absent rather than filled in.
- This is cosmetic information, not medical advice, and nothing here diagnoses or treats a health condition.
- Entry last updated 2026-09-02. Product-page methodology: the product library.