Wheezing is a loud, crackling whistling sound when you breathe. Many people with respiratory allergies know that wheezing often accompanies the hay fever season.  It can also be caused by a respiratory infection such as acute bronchitis. But chronic obstructive pulmonary disease (COPD) and asthma are the most common causes. Several treatments can reduce wheezing.  Your doctor should keep a close watch if you have asthma, severe allergies, chronic bronchitis, emphysema, or COPD. You may also need to see a specialist such as an allergist or pulmonologist. Anyone can get wheezing. This occurs most often in infants, possibly because of their smaller airways.  It is also common in children who have asthma or bronchiolitis. Adults who smoke or who have emphysema or heart failure are more likely to develop wheezing.