Interesting research
Hydrolyzed Protein
INCI: Hydrolyzed Keratin, Hydrolyzed Wheat Protein, Hydrolyzed Rice Protein · also protein hydrolysate, keratin peptides, wheat protein
Whole proteins chopped into fragments small enough to interact with hair. Keratin, wheat and rice are the common sources. Molecular weight is the variable that matters, and almost nobody puts it on the label.
Why it is here
Protein fragments that add body without weight. The one ingredient where more is documented to feel like straw, so we stopped at the studied amount.
Large fragments adsorb onto the hair surface and form a film that adds body and reduces friction. Small, low molecular weight fragments can penetrate into the fiber itself. Cationically modified hydrolysates are drawn to the negatively charged damaged sites the same way conditioning surfactants are. In combing tests, the best result comes from pairing a surface-active large fragment with a penetrating small one.
The receipt
Compound hydrolyzed proteins at 2 percent by weight gave a higher contact angle and lower frictional coefficient than a commercial protein-free control, and confocal imaging showed the proteins both adsorbing to the hair surface and penetrating into the fiber interior.
Transparent silicone-free shampoo containing proteins with strong hair conditioning properties. International Journal of Cosmetic Science, 2024. in vitro. PMID 37736006
In practice
- Typical use
- 0.5 to 3 percent, most often 1 to 2 percent. The published combing work used 2 percent total protein as a blend of a large cationic hydrolysate and a small penetrating one.
- Pairs with
- Behentrimonium Methosulfate, Panthenol, Cetearyl Alcohol
- Keep apart from
- Nothing chemically. The practical caution is dose: too much protein in a routine, with too little conditioning lipid alongside, is what people mean when they say their hair feels stiff or straw-like.
- Cautions
- Hydrolyzed wheat protein is a documented cause of contact urticaria and, in rare cases, of wheat-dependent allergy sensitized through skin rather than diet. If you have coeliac disease or a wheat allergy, choose a keratin or rice hydrolysate instead and read the label.
Questions people ask
Which hydrolyzed protein is best for hair?
Molecular weight matters more than source. The 2024 combing study got its best results from pairing a large cationically modified hydrolysate, which adsorbs to the surface, with a low molecular weight one that penetrates. Keratin has the most intuitive story since hair is keratin. Wheat and rice perform similarly and wheat carries an allergy caveat.
Can you get protein overload?
The phrase is folk vocabulary, not a clinical entity, but the underlying observation is real. Protein hydrolysates deposit a film and add stiffness. Enough of that without enough conditioning lipid alongside and hair feels rigid and snaps more easily. It is a formulation balance problem, not a disease, and it reverses.
Does hydrolyzed protein repair split ends?
No. Nothing does. A split end is a physically separated fiber and the only fix is scissors. What protein hydrolysates do is measurably lower friction and raise the contact angle, so hair combs with less force and splits less from the mechanical damage of combing. Prevention rather than reversal.