Asthma is a long term condition involving the respiratory tract. In asthmatics, the airways occasionally constrict, become inflamed, and can have excessive amounts of mucus, often in response to one or more triggers. Exacerbations may be triggered by such things as exposure to allergens, smoke (from tobacco or wood-burning fireplaces), cold or warm air, perfume, pet dander, moist air, exercise or exertion, or emotional stress. In kids, the most common triggers are viral illnesses such as those that cause the common cold. This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. The airway constriction responds to bronchodilators (i.e. albuterol) but these do not fix the inflammation. Between episodes, most patients feel well but can have mild symptoms and they may remain short of breath after exercise for longer periods of time than the unaffected individual. Asthma symptoms can range from mild to life-threatening but they can usually be controlled with a combination of medications and environmental changes.