Does a relaxer penetrates the medulla layer in the hair?

No, a relaxer does not penetrate the medulla layer of the hair. Hair consists of three main layers: the cuticle, cortex, and medulla. Relaxers primarily affect the cortex, where the hair's structure and texture are determined, by breaking down the disulfide bonds that give hair its shape. The medulla, which is the innermost layer, is not usually altered by chemical treatments like relaxers.