What do keratin, arginine and biotin actually do in this shampoo?

Hydrolysed keratin is keratin broken into low-molecular-weight fragments. Because the molecules are small, they can adhere to the uneven, lifted cuticle scales of damaged hair, filling microscopic gaps and cracks. This physical deposition makes the hair surface smoother, reduces inter-fibre friction (so strands slide past each other instead of tangling), and increases light reflection — which you perceive as shine. It does not penetrate the cortex or permanently rebuild the hair shaft; the effect is cosmetic and washes out over subsequent cleanses, which is why regular use maintains the benefit.

Arginine is an amino acid naturally present in hair keratin. In a rinse-off formula, its primary role is sensory and conditioning: it helps the shampoo feel less harsh and more cushioning during application, and it can support the hair’s surface hydration by attracting water molecules. It does not stimulate growth or reach the follicle from a shampoo contact time of 1–2 minutes.

Biotin (vitamin B7) is included as a cosmetic ingredient associated with normal hair structure. In leave-on scalp treatments, biotin may have a more direct role; in a rinse-off shampoo, its contribution is largely symbolic and supportive — part of a broader vitamin complex (with niacinamide, vitamins A and E) that signals a “care-oriented” formula. The measurable smoothing and manageability come mainly from the hydrolysed keratin, panthenol, and the light lipid layer from sunflower and peanut oil.

Together, these actives make the cleansing step itself contribute to hair condition rather than degrade it, which is the core purpose of this product category.