When you have asthma, inflammation and tightness around the airways in your lungs causes them to narrow (via the World Health Organization). This makes it harder to breathe, and causes you to cough, wheeze and experience tightness in your chest. Symptoms tend to be worse in the evening or when you exercise. Asthma can also be triggered by viral infections, smoke and fumes, pollen, pet dander, and strong odors from soaps and shampoos.
Breathing through your mouth can make asthma worse. Your nose serves a protective purpose, filtering the air you breathe and catching potential irritants before they can make their way to your lungs. This is facilitated by tiny hairs called cilia that line the mucous membranes of the nose. Breathing through your mouth bypasses this built-in air purifier and creates a direct pathway for irritants to your lungs, which can trigger an asthma attack.
Additionally, mouth breathing contributes to allergic rhinitis, a condition that affects one-sixth of the population and results in nasal congestion, post-nasal drip, and sneezing, among other symptoms (via NIH). According to an article in Allergy, Asthma & Clinical Immunology, people with allergic rhinitis are three times more likely develop asthma.
Asthma is a treatable condition, but it can also be deadly. According to the Asthma and Allergy Foundation of America, asthma kills an average of 10 people in the U.S. each day. Per a study in Asthma, mouth breathing potentially increases asthma-related mortality due to a greater sensitivity to inhaled allergens.
