The Olaplex No.4 Bond Maintenance Shampoo contains an ingredient called Bis-Aminoprophyl Dimaleate. This helps protect and repair damaged hair by repairing the disulfide bonds broken during chemical treatments. Products such as bleach, peroxide, perms and chemical straighteners damage hair at the molecular level, making hair more susceptible and vulnerable to breakage and tangles. This super ingredient helps to prevent this. In addition, the shampoo is enriched with acetic acid which is a great scalp cleanser.