Relaxer
A strong chemical cream that permanently straightens curly or coily hair by breaking its bonds.
Also: chemical straightener, perm (in some countries)
A relaxer is a chemical cream that straightens tightly curled or coily hair by breaking the bonds in the cortex so the hair can be smoothed flat. Lye relaxers contain sodium hydroxide; no-lye relaxers use other alkaline chemicals. Treated hair stays straight, and new growth is relaxed in touch-ups every few months. Relaxers were widely used from the mid-20th century; since the 2000s many people have stopped using them in the natural hair movement. Stylists handle them carefully because they can burn the scalp.