When hair is bleached, it goes through an oxidation process that dissolves the color pigments in the hair. According to Hollistics, during oxidation, bleach ingredients release oxygen molecules that bind to the hair's melanin pigment, eventually dissolving the pigment.
Bleach is a harsh ingredient that can strip hair of its essential oils, causing split ends and breakage. After bleaching, it is important to replace the moisture that has been removed from the hair. Regularly moisturizing hair processed with bleach helps decrease the damaging effects of the chemical. Deep conditioning treatments are recommended as a way to keep bleached hair healthy and moisturized.