Keratin is everywhere on the haircare shelf, and almost never explained. Here is what actually happens when you apply a product that contains it, and above all what the word hydrolysed changes on the label.
Your hair is already made of keratin
A hair is not a hollow tube: it is a dead protein fibre, made up mostly of keratin. The same family of proteins forms your nails and the outer layer of your skin. If you are starting from scratch on the subject, begin with our keratin guide, which explains its role and the causes of its breakdown.
This fibre is organised into two zones that matter here. The cortex, at the centre, holds the bulk of the keratin: it is what gives hair its strength and its elasticity. The cuticle, on the surface, is made of scales that overlap like roof tiles. When those scales lie flat, light reflects off them and hair looks shiny. When they lift, light scatters and hair looks dull, even when it is clean.
Colouring, bleaching, straighteners, hairdryers, friction against the pillow: each of these opens the cuticle a little further and costs the cortex some protein. It builds up, and it does not repair itself, because hair does not regenerate.
Why raw keratin is useless in a bottle
The idea seems obvious: if hair loses keratin, just put some back. The problem is physical.
Native keratin is a very large protein, barely soluble in water, and folded in on itself. As it is, it cannot cross the cuticle: it sits on top, rinses away, and does no more than a conventional film-forming ingredient.
This is where hydrolysis comes in. The process breaks the protein down into shorter fragments, peptides and amino acids, water-soluble and of much lower molecular weight. On an INCI list, the result has a precise name: Hydrolyzed Keratin. If you only read Keratin, it is not the same thing.
What a fragment of hydrolysed keratin does
- The shortest fragments diffuse into the fibre and settle in the depleted zones, where protein is missing.
- The longer fragments stay on the surface and help re-seal the lifted scales of the cuticle.
- Either way, the effect is temporary: it fades wash after wash. This is upkeep, not a permanent procedure.
That is also why regularity matters more than concentration. A product used every week does better than an overdosed one used once a quarter.
Keratin in a hair product and a keratin straightening treatment: unrelated
The confusion is common and worth clearing up, because the two have neither the same mechanism nor the same precautions.
| Hydrolysed keratin haircare | So-called "keratin" straightening | |
|---|---|---|
| What it is | An everyday cosmetic: shampoo, mask, leave-in | A technical service carried out in a salon |
| What acts | Keratin peptides that fill in and smooth the surface | High-temperature heat that reshapes the fibre |
| Effect on shape | None: a curl stays a curl | Lasting straightening for several weeks |
| How long it lasts | A few washes | Several months |
A hydrolysed keratin treatment does not straighten. It makes the fibre smoother to the touch and easier to style, which often gives the impression of better-behaved hair. The structure itself does not change.
Who it helps, and when it helps less
Hydrolysed keratin is most useful on hair that has lost protein: coloured or bleached hair, lengths exposed to heat, split ends, porous hair that soaks up water very fast and dries just as fast. If you are not sure where you stand, start with the porosity assessment.
There is, however, a balance point worth knowing about. Hair saturated with protein and short on moisturising agents can turn stiff, rough and brittle: this is what is known as protein overload. The signal is easy to spot, the hair paradoxically feels drier after the treatment than before. The fix is not to drop protein, but to pair it with ingredients that hold water, such as glycerin or Sodium PCA, and with lipids.
That is the principle behind the formulas in the KERA NEXT range: hydrolysed keratin never works alone in them.
Where cosmetic keratin comes from
Almost always from an animal source, most often sheep's wool or feathers. It is rarely mentioned, and it has a direct consequence: a keratin treatment is not vegan. Plant-based alternatives and their real limits are compared in hydrolysed keratin or plant keratin.
At KERA NEXT, the hydrolysed keratin comes from sheep's wool, an origin confirmed in writing by our manufacturer, who is the responsible person for the product under European regulation. All four formulas are certified COSMOS NATURAL by ECOCERT Greenlife, contain between 98 and 99% ingredients of natural origin, and the COSMOS standard prohibits raw materials extracted from live or slaughtered animals.
How to fit it into a routine
No need to pile things on. Three steps are enough, in this order.
- At washing. A hydrolysed keratin shampoo lays down a first dose during cleansing, then a conditioner closes the cuticle back down on mid-lengths and ends.
- Once or twice a week. The intensive repair mask delivers the most concentrated dose, left on for 5 to 10 minutes on clean, damp hair.
- Every day. The leave-in mist is spritzed onto damp hair and stays in the fibre. This is the step that maintains the result between two masks.
Give it three to four weeks before judging. Hair grows about a centimetre a month: what you are assessing is not new growth, it is the condition of the lengths already there. How it fits together with the rest of your care is set out in our four-step routine.
Hydrolysed keratin: the essentials
- On the label, look for Hydrolyzed Keratin. "Keratin" on its own does not have the same effect.
- Hydrolysis exists to shrink the protein so that it can cross the cuticle.
- The effect lasts a few washes: regularity beats concentration.
- A keratin treatment does not straighten and has nothing to do with a salon straightening service.
- Too much protein without moisture leaves hair stiff and brittle.
- Cosmetic keratin is of animal origin: these products are not vegan.
Frequently asked questions
Does hydrolysed keratin make hair grow?
No. Growth happens at the follicle, beneath the scalp, and a product applied along the length has no access to it. That said, a less brittle fibre holds on to its length better, which can give the impression of faster growth.
Is it suitable for coloured hair?
That is in fact one of the cases where it is most useful, since colouring weakens the cuticle and depletes the cortex.
Can it be used on curly or coily hair?
Yes, with no effect on the shape of the curl. As these textures are often more porous, the protein and moisture balance rule matters even more here.
How long does the effect last?
A few washes. Hydrolysed keratin is gradually washed out, which is why regular use beats occasional use.
Does a keratin treatment contain formaldehyde?
An everyday cosmetic, no. Formaldehyde and its releasers are associated with certain salon straightening services, which belong to an entirely different product category. COSMOS-certified formulas exclude these substances.
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.