Proteins & Hair
Hydrolysed proteins and peptides, and what "repair" means cosmetically.
Last reviewed by the Hairavie editorial team on September 1, 2026.
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What's in the bottle
Cosmetic protein ingredients are usually hydrolysed — broken into smaller fragments and peptides so they can interact with the fibre. You'll see wheat, soy, silk, keratin and rice among others.
Fragment size influences behaviour: smaller fragments may interact more readily with the fibre, larger ones tend to act more at the surface.
What they can do
- Temporarily improve tensile behaviour of damaged fibre
- Add a conditioning film that improves smoothness
- Reduce combing friction
- Make chemically processed hair feel less limp or mushy
What they cannot do
They do not biologically heal hair. The fibre is not living tissue, and no topical protein restores it to its original state.
Effects wash out and need reapplication. That's a normal cosmetic result, not a failure.
Protein and moisture are not a battle
Popular framing treats these as opposing forces you must balance on a knife edge. In practice, conditioning need and strength need are separate questions, and dryness never implies a protein requirement.
Hairavie keeps them as two independent readings for exactly that reason.
If hair feels stiff or brittle after repeated protein-heavy products, easing off is reasonable — but that's your observed result, not a universal rule.
How Hairavie knows this
Hairavie cites peer-reviewed research, scientific reviews, reference textbooks, dermatology organisations and government health resources. Beauty blogs are never used as scientific authority.
- Cosmetic science literatureFernandes, M. M. et al. (2012). Keratin-based peptide: biological evaluation and strengthening properties on relaxed hair. International Journal of Cosmetic Science
- Reference textbookRobbins, C. R. (2012). Chemical and Physical Behavior of Human Hair (5th ed.). Springer
- Scientific reviewGavazzoni Dias, M. F. R. (2015). Hair cosmetics: an overview. International Journal of Trichology
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