“The purpose of brushing your hair is to make it look neat, remove tangles, and smooth out each strand,” says Tsippora Shainhouse, M.D., board-certified dermatologist in Beverly Hills. But if there’s a buildup of dead hair between the bristles, they can’t properly pass through your strands, which makes the act of brushing your hair…well, pointless. It can also put your hair at risk for damage: As you brush, your strands can snag on bits of dried product and cause breakage.