Repair Intensive Repair Mask is a deeply restorative mask that repairs and restructures damaged and over-processed hair. Over time, seemingly innocuous processes like brushing and heat styling can cause serious harm to the hair fiber. This happens when keratin, the natural protein that makes up 95% of the hair fiber, is so severely damaged that it fails to perform its function. On healthy hair, keratin lends the hair its elasticity and shine; damaged hair loses both of these attributes, and, as a result, begins to look dull and coarse.