What Hydrolysed Keratin Actually Is
Keratin is the main structural protein of the hair strand and makes up most of the cortex, the inner layer that carries its strength. In its natural form the molecule is far too large to get inside the strand.
What “hydrolysed” means
Hydrolysis breaks the large protein molecule into smaller fragments, peptides and amino acids. Those smaller pieces are what can reach the inside of a damaged strand. The lower the molecular weight, the deeper they travel, and the shorter the effect lasts.
How It Works on Hair
Damaged hair has cracks and gaps on the surface and within the cortex. They come from colouring, bleaching, heat and mechanical friction, covered in detail in our article on hair damage. Keratin fragments lodge in those gaps and fill them temporarily.
Why the effect is temporary
The strand outside the scalp is a dead structure and cannot repair itself. Keratin fragments do not bond permanently with it; they sit mechanically and wash away gradually with each shampoo. That is why the result is maintained by regular use rather than achieved once and for all.
What Actually Changes
Hair combs through more easily, breaks less during brushing and styling, looks denser and reflects light better. Those changes are visible and tangible, but they are cosmetic: the condition of the existing strand improves, not the structure it grew with.
What it cannot do
Glue a strand that has already snapped, remove split ends, or change your natural texture. Split ends are solved with scissors and nothing else. A product promising otherwise is promising more than is possible.
Who It Suits
The clearest benefit goes to coloured and bleached hair, hair after chemical services, and hair that meets heat tools often. Healthy, untouched hair has fewer gaps to fill and notices correspondingly less difference.
When protein becomes too much
The opposite extreme exists too. With protein treatments used too often and not enough moisture alongside, hair can turn stiff, feel dry and become more prone to snapping. The balance between protein and moisture matters more than the amount of either.
How to Use It
In a mask or intensive treatment once a week is a sensible start for damaged hair. Heavily bleached hair can take twice, but watch how it responds: if it starts to feel dry and inflexible, alternate with a purely moisturising mask. How this fits the wider regime is covered in our hair care routine.
What to Look For on the Label
On an ingredient list it appears as hydrolyzed keratin, and sometimes as hydrolyzed wheat protein or hydrolyzed silk when the source is plant or silk. Its position hints at the quantity: the further up, the more there is.
Molecular weight
If the manufacturer states it, that is useful information. A lower weight means deeper penetration and a more noticeable sense of strength from within. A higher one stays on the surface and gives more shine and body. Good formulas often combine both.
How to Tell It Is Working
The first sign is detangling: the comb moves through more easily and leaves fewer hairs behind. After a few applications hair usually looks denser and reflects light more evenly.
The opposite sign matters just as much. If hair starts to feel stiff and straw-like and breaks more than before, that is protein overload. Pause for two or three weeks and lean on moisturising masks before returning to protein care.
Keratin pairs well with humectants and with oils that seal on top. You will find products in our hair care collection.
