Keratin is a protein and the major component in hair, skin and nails; in fact, hair is mainly comprised of keratin-associated proteins. Keratin acts both as an external protective protein in the cuticle (the outer layers of a hair strand) and as an internal structural protein in the cortex (the inner core of the hair that helps determine its strength).
Keratin depletes when hair is damaged physically, chemically and/or from environmental factors, such as the sun. This keratin loss exposes the hair’s cortex, making it susceptible to additional damage, and causes porous spots to develop—like potholes in a road. Replenishing lost keratin helps correct porosity and smooth the hair’s surface. It restores strength and elasticity—giving the hair a more youthful, healthy appearance.