Asthma is a chronic disease involving the airways in the lungs. These airways, or bronchial tubes, allow air to come in and out of the lungs. If you have asthma your airways are always inflamed. They become even more swollen and the muscles around the airways can tighten when something triggers your symptoms. This makes it difficult for air to move in and our of the lungs, causing symptoms such as coughing, wheezing, shortness of breath and/or chest tightness.

Asthma symptoms, also called asthma flare-ups or asthma attacks, are often caused by allergies and exposure to allergens such as pet danger, dust mites, pollen or mold. Non-allergic triggers include smoke, pollution or cold air or changes in weather.

Asthma, American Academy of Allergy Asthma & Immunology, http://www.aaaai.org/conditions-and-treatments/asthma