Many men in Western cultures are accustomed to shave their facial hair, so only a minority of men reveal a beard, even though fast-growing facial hair must be shaved daily to achieve a clean-shaven or beardless appearance. Some men shave because they cannot genetically grow a "full" beard (generally defined as an even density from cheeks to neck), their beard color is genetically different from their scalp hair color, or because their facial hair grows in many directions, making a groomed or contoured appearance difficult to achieve. Some men shave because their beard growth is very excessive, unpleasant, or coarse, causing skin irritation. Some men grow a beard or moustache from time to time to change their appearance or visual style.