A nasal breathing aid comprising the following components: a housing； facial engagement means attached thereto； at least two nostril pieces coupled to the housing. On the housing, there are at least two nasal inlets； at least one vent； and in the housing: a first passage and a second passage, each communicating an inlet with a vent, and fluid-isolated from each other, and restriction means configured to allow free flow of air through each passage from a vent to an inlet, and flow of air through the first passage independently restricted from flow of air through the second passage, from an inlet to a vent.
