Final answer:
The three common types of chemical hair relaxers are thio relaxers, alkaline (lye) relaxers, and no-lye relaxers, each utilizing different chemical compounds such as thioglycolate, sodium hydroxide, and calcium or guanidine hydroxide.
Step-by-step explanation:
The most common types of chemical hair relaxers are thio relaxers, alkaline (lye) relaxers, and no-lye relaxers. Chemical hair relaxers are products used to permanently straighten or 'relax' naturally curly or coiled hair textures. Thio relaxers use thioglycolate compounds as the reducing agent. Alkaline relaxers, also known as 'lye' relaxers, contain sodium hydroxide as the active ingredient which effectively straightens hair by breaking down disulfide bonds within the hair's structure. Finally, no-lye relaxers use calcium hydroxide or guanidine hydroxide, which are gentler on the scalp than lye-based relaxers but can be equally effective at straightening hair.