Open mouth breathing refers to breathing while the lips are parted or open.  In this way of breathing, the individual does not use, or uses very little, the nose to inhale and exhale the air.  Open mouth breathing is considered rescue breathing and encourages the body to stay in a state of “fight or flight.”  During this state the body must prioritize the most important functions for survival.  Functions like digestion, growth hormone production and being able to concentrate are put on hold.