Keratin is a protein and the major component in skin, hair and nails; in fact, the 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 is depleted 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—much like potholes in a road. Replenishing lost keratin helps to correct porosity and smooth the hair’s surface. It restores strength and elasticity, giving the hair a more youthful, healthy appearance.