Phytokeratin, a plant-based alternative to keratin, is often found in hair care products as well as in formulations for eyelashes and eyebrows. But what benefits does this active ingredient offer to hair, lashes and brows? Discover them in this article.
Hair, lashes and brows: the benefits of phytokeratin?
Summary
Published on August 13, 2025, by Sandrine, Scientific Editor — 7 min of reading
Themes:
A closer look at the keratin present in hair, eyelashes and eyebrows.
Keratin is a fibrous protein organised into hierarchical structures, forming microfibrils in the cortex of hair, eyelashes, eyebrows and other body hairs. This structured organisation underlies the strength of hair : in theory, if the scalp allowed it, a head of about 120,000 hairs could support a weight of 12 tonnes. Keratin consists of chains of amino acids, with a high proportion of cysteine, a sulphur-containing amino acid. The thiol groups (–SH) of cysteine can oxidise to form disulphide bonds (–S–S–), which act as bridges between keratin chains. These disulphide bonds are essential to the cohesion and stability of the hair fibre.
Keratin is also highly prevalent in the cuticle, the outermost layer of hair, eyelashes and eyebrows. Composed of keratinised, scale-like cells, the cuticle acts as a protective barrier. The alignment of these cells is essential: when disrupted, the fibre becomes more vulnerable. External aggressors such as UV radiation, heat or chemical treatments can then degrade keratin, undermine the cohesion of the cuticle and promote dehydration, breakage or even the shedding of body hair and scalp hair.
Did you know? The disulphide bonds in keratin can be altered. This principle underpins hair straightening and perming techniques. These techniques break the disulphide bonds to reshape the hair, which is then fixed during re-oxidation.
The importance of keratin for hair, eyelashes and eyebrows.
Source: KWON I. K. & al. Human hair keratin and its-based biomaterials for biomedical applications. Tissue Engineering and Regenerative Medicine (2014).
Phytokeratin, a plant-derived active ingredient of interest for caring for hair, eyelashes and eyebrows?
As keratin is fundamental to the integrity of hair fibres, it is no surprise that it is so often used in cosmetics. This active ingredient, however, is of animal origin (for example, found in feathers, wool or hooves), which can deter some people. To address this problem, the phytokeratin was developed. It is a natural alternative obtained by the hydrolysis of plant proteins, such as wheat or almond, which has an amino acid structure close to that of animal keratin. Through biomimicry, plant keratin could reproduce the effects of animal keratin.
Nevertheless, it is important to note that the phytokeratin is a relatively recent active ingredient in the cosmetics industry. To date, no clinical study has directly assessed its effects on the hair fibre or on the hairs of the eyelashes and eyebrows. However, its biochemical analogy with animal keratin suggests it may offer similar benefits and that it could in particular hydrate eyelashes, eyebrows and hair. Indeed, phytokeratin contains several hydrophilic amino acids, including glutamine, serine and threonine, which can bind to the surface of the hair fibre or hair shaft and form a protective film. Better protected, the fibres are less prone to breakage.
Besides its moisturizing properties, phytokeratin could offer a broader protective effect, particularly against environmental aggressors such as the UV rays. Although no study has yet evaluated this effect for phytokeratin, findings obtained with a hydrolysed form of animal keratin allow us to propose certain hypotheses. A recent investigation demonstrated the photoprotective effects of hydrolysed keratin on hair fibres. Researchers exposed strands of hair to continuous irradiation simulating accelerated solar ageing after pre-treating them, or not, with a solution containing hydrolysed keratin. Untreated hair showed a significant loss of mechanical strength (−14.32% tensile resistance), whereas hair treated with hydrolysed keratin was not only protected from this degradation but also saw their rigidity increase by 21.66% after exposure. Although phytokeratin differs from animal keratin, it also comprises small amino-acid chains derived from a hydrolysis process: it could therefore exhibit a comparable effect.
Phytokeratin may form a protective film on the surface of fibres that absorbs part of the UV radiation and, as it degrades, releases peptide fragments which penetrate the fibre to reinforce its internal structure.
Photoprotection of hair using hydrolysed keratin.
Source: CHANG K. & al. Performance and mechanism of hydrolyzed keratin for hair photoaging prevention. Molecules (2025).
The question of the efficacy of keratin, whether of animal or plant origin, largely depends on its ability to interact with the hair fibre. A recent study on curly hair, which had been previously relaxed with a sodium hydroxide solution, evaluated the influence of hydrolysed keratin peptides of different molecular sizes on the hair’s physical properties. Three fractions were tested: low molecular weight keratin (≈ 221 Da), medium molecular weight keratin (≈ 2 577 Da), high molecular weight keratin (≈ 75 440 Da), as well as a reference amino acid (L-leucine, 131 Da).
The results demonstrate that low- and medium-molecular-weight peptides are capable of penetrating the hair cortex, whereas high-molecular-weight peptides predominantly bind to the surface, with penetration limited to the outer layers. This internal penetration was confirmed by cross-sectional analysis of the fibres: at ambient humidity, hair treated with 1 % low-molecular-weight peptides or 1 % leucine exhibited a significant increase in diameter compared with control hair (respectively +11.7 % and +11.0 % relative to the relaxed control). This increase in cross-section indicates interaction with internal protein structures and provides strong evidence of cortical penetration.
From a mechanical standpoint, medium- and high-molecular-weight peptides significantly increased the Young’s modulus and reduced fibre breakage, both at low (20%) and high (80%) humidity. At 20% humidity, the tensile strength increased by approximately 18.6% for medium-molecular-weight peptides and by 16.3% for high-molecular-weight peptides compared with the straightened control.
Breaking stress measured at 20% and 80% relative humidity as a function of treatment and hair condition.
Source: HINDLEY M. & al. Penetration of different molecular weight hydrolysed keratins into hair fibres and their effects on the physical properties of textured hair. International Journal of Cosmetic Science (2020).
These data suggest that molecular weight influences not only penetration depth but also the mode of action. Light keratin peptides may penetrate the hair fibre and act from within to reinforce it, potentially by re-forming hydrogen bonds broken as a result of external damage. Heavy keratin peptides would act primarily at the surface, filling in cuticle irregularities and limiting further harm. Phytokeratin, having a molecular structure akin to that of keratin, can by analogy be expected to exhibit similar mechanisms of action.
Sources
KWON I. K. & al. Human hair keratin and its-based biomaterials for biomedical applications. Tissue Engineering and Regenerative Medicine (2014).
MEYERS M. A. & al. Structure and mechanical behavior of human hair. Materials Science and Engineering (2017).
HINDLEY M. & al. Penetration of different molecular weight hydrolysed keratins into hair fibres and their effects on the physical properties of textured hair. International Journal of Cosmetic Science (2020).
HWANG Y.-S. & al. Keratin-mediated hair growth and its underlying biological mechanism. Communications Biology (2022).
CHANG K. & al. Performance and mechanism of hydrolyzed keratin for hair photoaging prevention. Molecules (2025).
