Keratin

The structural protein your hair is made of, and the key to repairing it

What Is Keratin?

Keratin is the primary structural protein of human hair, nails, and the outer layer of skin. Hair is approximately 95% keratin by composition. Each strand of hair is built from a cortex of keratin fibers organized in a precise helical arrangement, protected by an outer cuticle layer of overlapping keratin scales. When hair is healthy, the cuticle lies flat, reflecting light evenly and allowing the cortex proteins to remain intact. When hair is damaged, the cuticle lifts or breaks, exposing the cortex to further degradation and producing the dryness, frizz, and breakage that characterize chemically treated or heat-damaged hair.

Cosmetic keratin treatments work by delivering hydrolyzed keratin, which is keratin broken down into smaller peptide fragments, into the gaps and disruptions in damaged hair's structure. These fragments bind to the cortex and cuticle, filling in areas of protein loss, smoothing the cuticle surface, and reinforcing the fiber's structural integrity. The result is hair that is measurably stronger, smoother, and more resistant to further damage.

Hydrolyzed keratin used in cosmetics is typically derived from wool, feathers, or other keratin-rich biological sources and processed to reduce molecular size for penetration into the hair shaft. The hydrolysis process is important: intact keratin molecules are too large to enter the hair fiber, while hydrolyzed fragments are small enough to penetrate the cortex and create lasting repair effects rather than sitting entirely on the surface.

Key Benefits

• Repairs and fills structural gaps in damaged hair fibers, restoring strength and resilience
• Smooths the hair cuticle to reduce frizz and improve light reflection (shine)
• Reduces breakage from mechanical stresses including brushing, heat styling, and washing
• Improves manageability and reduces tangles by improving cuticle alignment
• Provides thermal protection when used before heat styling by reinforcing the hair's protein structure
• Particularly effective for chemically treated, bleached, or repeatedly heat-styled hair

How nuréo Uses Keratin

Hydrolyzed keratin is the core active in our Keratin Leave-In Hair Mist ($24). We chose a leave-in mist format specifically because it allows the keratin to remain on the hair rather than being rinsed away before it can do its work. The mist format also makes the product lightweight enough to use on fine or low-porosity hair without creating heaviness or buildup, a common problem with heavier keratin creams and serums.

The leave-in mist is designed to be applied after washing and before heat styling or air drying, positioning the keratin peptides for maximum repair benefit during the mechanical stress of detangling and styling. It also serves as a daily detangler and frizz-control product between wash days.

How to Use

Apply the Keratin Leave-In Hair Mist to clean, towel-dried hair after washing. Hold the bottle 6 to 8 inches from the hair and mist evenly across the lengths, focusing on the mid-shaft and ends where damage typically concentrates. Comb through gently to distribute. Proceed with your usual styling routine. The product can be used before air drying or before heat tools.

For a targeted repair treatment, apply a slightly heavier amount to particularly damaged sections, such as bleached ends or areas with significant breakage, and allow to air dry without heat. Between wash days, the mist can be used to refresh and smooth without re-wetting the hair fully, which reduces friction-related breakage from dry hair combing.

Frequently Asked Questions

Repair and strengthen damaged hair from the inside out.