All hair types (natural, curly, fine, straight, etc.) derive most of their integrity from healthy, properly paired, disulfide bonds. When hair is damaged via thermal, chemical, mechanical or environmental factors, these disulfide bonds are broken apart resulting in single sulfur hydrogen bonds.
There are two reactions that can take place after these bonds break. The first reaction is that the single sulfur hydrogen component pairs with a single oxygen molecule. This makes a perfect pair with no further damage taking place.
The second reaction is where damage occurs. A single sulfur hydrogen molecule will pair with three oxygen molecules creating S03, or what is known as a sulfate group. The protonated sulfate is known as Cysteic Acid. Cysteic acid then eats the protein out of the hair.
In the case of chemical services, OLAPLEX works by pairing with the single sulfur hydrogen bond faster than the three oxygen molecules can, and protects your hair from damage.