From the way the girls in the beauty shop talk, it seems like it's all about lye versus no-lye relaxers. Not true: Thio relaxers also straighten hair, using ammonium thioglycolate, a chemical that also creates permanent waves. Thio relaxers are milder than the other types so work well for divas with naturally loose curls, frizzy or fine hair.
Thio relaxers chemically straighten the hair, just like lye and no-lye relaxers. Thio relaxers typically come in a cream or gel formation. These relaxers soften the hair and loosen cystine links between disulfide bonds in your hair. Because disulfide bonds make curls, this gets you straight locks. During the neutralizing phase, the disulfide bonds are reformed but your hair remains straight. With both lye and no-lye relaxers, disulfide bonds remain broken.
Thio relaxers contain ammonium thioglycolate or ATG, hence the nickname of "thio." They have a relatively low alkaline content with a pH of 9 to 10. Lye relaxers contain sodium hydroxide and have a pH of 13. No-lye relaxers have guanidine hydroxide as their active ingredients; they also have a pH of 13.
Because of the low pH, thio relaxers are milder than their hydroxide counterparts. For this reason, some consider thio relaxers safer than lye or no-lye types and believe that the risk of damage to the hair is less. Just like hydroxide relaxers, thio relaxers must be neutralized after processing. Thio relaxers use hydrogen peroxide or sodium bromate to neutralize the ammonium thioglycolate.
Switching from a lye or no-lye relaxer to a thio relaxer leads to major stress for your hair. If you overlap the different types of chemicals in your hair, strands will break. Thio relaxers process a bit differently than other types. When washing out a thio relaxer, wash about half of the relaxer cream from your strands using warm water. Comb your hair -- which can still appear wavy -- smooth and straight and give the cream five more minutes of processing time. Rinse out the rest of the thio relaxer and apply the neutralizer. As long as you get strands straight in the combing, the hair will stay straight.