They say that prickles of holly leaves prevent Oni (ogre) from entering through the door by piercing Oni's eyes, and that the smell of sardine chases Oni away (on the contrary, another explanation is that the smell of sardine invites Oni to approach and then prickles of holly leaves pierce Oni's eyes).
柊の葉の棘が鬼の目を刺すので門口から鬼が入れず、また鰯の臭いで鬼が近寄らないと言う（逆に、鰯の臭いで鬼を誘い、柊の葉の棘が鬼の目をさすとも説明される）。