Why Mouth-breathing is bad
Slides courtesy of Dr German Ramirez-Yanez (DDS, MDSc, PhD)
Your body is designed for air to enter and exit via your nose. The air coming through your nose is filtered, warmed and moistened making it suitable for your airways and lungs. If not filtered, bacteria, viruses and other irritants will contribute to enlarged tonsils and adenoids, sinusitis, blocked noses and ear infections.
When you breathe through your nose your tongue should rest on the palate. In a growing child, the tongue will develop a nice broad palate which will create plenty of room to fit your teeth. As the palate is the floor of the nose, it also develops a large nasal airway allowing you to take in more air. If you breathe through your mouth your tongue must drop down from the palate to allow air to pass - nothing is supporting the development of the palate and the cheek muscles are no longer relaxed and push in against the teeth causing narrowing of the palate and crowded teeth.