Keratin is an exclusively animal protein: no plant produces it. What the market calls "plant keratin" or "phytokeratin" actually refers to hydrolysed plant proteins, from wheat, soy or rice, chosen to mimic the amino acid profile of keratin. They are good actives, but they are not the same thing, and they do not do exactly the same job.
The comparison in one table
| Hydrolysed keratin | Hydrolysed plant proteins | |
|---|---|---|
| Origin | Animal (wool, feathers) | Plant (wheat, soy, rice, oat) |
| INCI name | Hydrolyzed Keratin | Hydrolyzed Wheat / Soy / Rice Protein |
| Cystine content | High, like hair | Low |
| Main strength | Structural repair of the cortex | Coating, moisture, lightness |
| Vegan | No | Yes |
| Priority use case | Very damaged, bleached, porous hair | Fine, slightly sensitised hair, prevention |
Hydrolysed keratin: the hair's own protein
This is genuine keratin, the same family of proteins that makes up the fibre, broken down by hydrolysis into peptides small enough to cross the cuticle.
Its strength comes down to one word: affinity. Its amino acid composition, and in particular its cystine content, the sulphur-containing amino acid that forms disulphide bridges, is that of hair itself. It therefore integrates into damaged zones with a compatibility that plant proteins cannot match, since wheat and soy are naturally low in cystine.
The full mechanism, its limits and how long the effect really lasts are set out in our article on hydrolysed keratin.
Plant keratin: a name that needs decoding
Keratin is produced by the keratinocytes of mammals, birds and reptiles. No plant synthesises it. The label "plant keratin" is therefore a marketing shorthand, not a chemical reality.
That does not mean the ingredient is of no interest. Once hydrolysed, plant proteins bind to the fibre, coat it, hold moisture in and improve softness and strength. Depending on peptide size, they penetrate slightly or form a protective film on the surface. That is exactly the role of the wheat proteins in the /REPAIR Mask, alongside keratin.
The fair way to put it: a talented impersonator, not the original.
The ethical question, head on
If plant-based claims are riding high, it is also for legitimate ethical reasons. Two clarifications to help you choose with your eyes open.
- Cosmetic keratin comes from by-products of existing supply chains, mainly shorn wool. No animal is bred or slaughtered to produce it.
- The quality of sourcing varies a great deal from one supplier to another. This is where certifications play a role, by governing origin and processing methods: see our breakdown of COSMOS NATURAL certification.
For vegans, the choice is nonetheless clear: only plant proteins are suitable. A keratin treatment, even certified and not tested on animals, is not vegan. That means accepting a compromise on deep repair, or making up for it with a more diligent routine.
How to choose for your hair
- Very damaged, bleached or very porous hair: hydrolysed keratin comes first. Check for "Hydrolyzed Keratin" in the INCI list, ideally in a mask.
- Fine or slightly sensitised hair: either works. A formula combining both families is ideal.
- Normal hair: regular, moderate exposure through shampoo and conditioner is enough to maintain your protein capital.
- In every case: proteins repair, but excess stiffens. Always alternate with moisture, and cut back the frequency if your hair turns stiff and brittle despite the care.
To place your own profile, take the porosity test, then settle into the 4-step routine.
The two keratins: the essentials
- Keratin is exclusively animal. Plant keratin does not exist in the chemical sense.
- On the label, look for "Hydrolyzed Keratin" for the real thing, "Hydrolyzed Wheat Protein" for the alternative.
- Keratin repairs the structure, plant proteins coat and moisturise.
- The two work very well together in a single formula.
- No keratin treatment is vegan, even a naturally certified one.
Frequently asked questions about types of keratin
Does plant keratin really exist?
In the chemical sense, no: keratin is an exclusively animal protein. The term refers to hydrolysed plant proteins chosen to mimic its amino acid profile. They are quality actives, but different ones.
Does cosmetic keratin involve harming animals?
It comes from by-products of existing supply chains, mainly shorn wool. No animal is bred for it. It is not, however, vegan, unlike plant proteins.
How do I recognise real keratin on a label?
Look for "Hydrolyzed Keratin" in the INCI list. The entries "Hydrolyzed Wheat Protein", "Hydrolyzed Soy Protein" or "Hydrolyzed Rice Protein" indicate plant proteins, even if the front of the bottle talks about plant keratin.
Can you use both together?
Yes, and it is the most interesting combination: keratin repairs the structure while plant proteins coat and moisturise the surface.
Is plant keratin enough on very damaged hair?
It helps, but its low content of sulphur-containing amino acids limits its ability to rebuild the deeper structure. On a very damaged fibre, hydrolysed keratin remains the reference active.
Can too much protein damage hair?
Prolonged excess, whatever the source, stiffens the fibre and makes it brittle: that is protein overload. Stick to the frequencies, one or two masks a week, and alternate with moisturising care.
Sources
- Robbins C. R., Chemical and Physical Behavior of Human Hair, 5th edition, Springer, 2012.
- Gavazzoni Dias M. F. R., "Hair Cosmetics: An Overview", International Journal of Trichology, 2015.
Article written by the KERA NEXT editorial team. Individual results: the outcome may vary depending on the nature and condition of your hair.