Hair-straightening chemicals, especially in "home-made" solutions, are capable of causing chemical injury to the scalp and destruction of hair follicles with scalp scarring. Chemicals that can soften the strong fibers of the hair shaft are potent enough to injure scalp skin.
Hair bleaches can injure scalp skin, especially with recurrent use.
Permanent waving solutions may cause scalp injury, especially with frequent recurrent use.
Hair Loss and Its Causes