A Highly Resistant Structure Between the Cuticle and the Cortex of Human Hair. II. CARB, a Penetration Barrier

The study identified a highly resistant structure at the interface between the cuticle and the cortex of human hair, which acts as a penetration barrier. This structure, named CARB (cuticle anchored resistant base), was found to be located beneath the endocuticle of the innermost cuticle cell layer. The research showed that the penetration depth of a dye into the cortex did not correlate with the number of cuticle layers in partially decuticled hair but increased significantly when the last cuticle layer was lost. The cell membrane complex's denaturation did not affect dye penetration, indicating that CARB, not the cell membrane complex, serves as the primary barrier.