Is there a difference between nasal & oral/mouth breathing?

Yes, when breathing is done through the nose, the air is filtered (cleaned), warmed and humidified, and thus it reaches the lungs with less impurities that are in the air. When you breathe through your mouth the air does not go through this process and reaches the lungs full of impurities. The oral rest posture of the tongue and the mandible when mouth breathing may also alter mandibular posture, palate width, and other craniofacial growth patterns as well as posture of the head, neck, and upper body.