Hair irons and hot combs can only temporarily modify hair texture, whereas relaxers and the other methods permanently alter the structure of the hair, although new hair growth is not affected. The drug interferon alpha has been shown to modify hair follicles causing permanent change in a person's hair texture.

During much of the 20th century, social norms encouraged African-Americans to straighten the tightly curled texture of their natural hair, resulting in artificial styles such as the conk. Although straightened hair was generally considered a black hair style and not copying whites, as part of the Black Power movement in the 1960s, unstraightened hairstyles such as the Afro and dreadlocks became more widely accepted. Nevertheless, many African-American women still continue to straighten their hair as an aesthetic choice.

Hair straightening became more popular in the United States during the mid-late 1990s and through to the 2000s, whereas perming and curlier hair had previously been more popular fashions during the 1980s, even among men (for example, hair metal bands). However, both straight and wavy/curly hair can be achieved with use of a hair iron, and so it may be said that both straight and curly or wavy hair styles co-exist in modern fashion.