The historical dictum to brush hair with one hundred strokes every day is somewhat archaic, dating from a time when hair was washed less frequently; the brushstrokes would spread the scalp's natural oils down through the hair, creating a protective effect. Now, however, this does not apply when the natural oils have been washed off by frequent shampoos. Also, hairbrushes are now usually made with rigid plastic bristles instead of the natural boar's bristles that were once standard; the plastic bristles increase the likelihood of actually injuring the scalp and hair with excessively vigorous brushing. However, traditional brushes with boar's bristles are still commonly used among African Americans and those with coarse or kinky textures to soften and lay down curls and waves.