Nose breathing, an aid to better asthma control. Perhaps the simplest advice is to try to always breathe through the nose. Why? Because the nose functions to deliver air to the lungs in as perfect condition as possible. It makes over-breathing physically more difficult simply because of the smaller size of the nostrils compared with an open mouth, it filters out most of the dust and particulates found in the atmosphere, it moisturizes the air when it's dry, as in centrally heated rooms, delivering air that doesn't irritate and dry out the delicate membranes of the lungs, it conserves water and helps reduce the risk of dehydration, it contains active organisms that trap and destroy many potential infective agents in the air we breathe, protecting the lungs from infection, it is also found to be responsible for the production of up to 50% of nitric oxide in our body when we breathe normally through our nose. Nitric oxide has many vital functions in the body that are still being discovered, we know nitric oxide can dilate blood vessels and improve circulation hence its use for treatment in angina.