(See also Wheezing in adults.)
Wheezing is caused by a narrowing or blockage (obstruction) of the airways. The narrowing can be caused by one or more of the following:
Recurring episodes of wheezing are common in the first few years of life. Until recently, doctors diagnosed these episodes as asthma because, like asthma, episodes could be relieved by inhaling drugs that open the airways (bronchodilators) and because most adults who have asthma first developed symptoms in childhood. Now, however, doctors know that only some infants and young children who have such episodes of wheezing have asthma in later childhood or adolescence.
Children who are more likely to be eventually diagnosed with asthma include children who have one or more of the following risk factors:
Certain rashes (such as eczema)
More severe wheezing episodes
Family members with asthma
A family tendency to have many allergies
However, in most children, wheezing episodes stop by 6 to 10 years of age, and doctors do not diagnose these children as having asthma. Such children have other causes for their recurring episodes of wheezing.
The most common cause of a single, sudden episode of wheezing in infants and young children is usually a
The most common causes of recurring episodes of wheezing are
Less common causes of recurring wheezing include chronic difficulty swallowing that causes recurring inhalation of food or liquids into the lungs, gastroesophageal reflux, a foreign object in the lungs, or heart failure. Often, the cause of recurring wheezing is unclear.
Whatever the initial cause of the wheezing, symptoms are often worsened by allergies or inhaled irritants (such as tobacco smoke).
Wheezing is often accompanied by a recurring cough that is dry or brings up sputum (also called phlegm). Other symptoms depend on the cause and may include fever, runny nose, and feeding difficulties (caused by heart failure or difficulty swallowing).
A high-pitched wheezing sound is heard when the child breathes out. If airway narrowing is severe, the wheezing sound can be heard when the child breathes in. Very ill children may also breathe rapidly, use a lot of their chest muscles to breathe, and have flaring of the nostrils and a bluish discoloration of the skin (cyanosis). Fever may be present in children with a lung infection.
For a first episode of severe wheezing, most doctors do a chest x-ray to look for signs of a foreign object in the lungs, pneumonia, or heart failure. Doctors measure oxygen levels in the blood by placing a sensor on a finger (pulse oximetry).
For children with recurring episodes of wheezing, flare-ups typically do not require testing unless there are signs of severe breathing problems. Children who have frequent or severe flare-ups or symptoms that are not relieved by bronchodilators or other asthma drugs may need other tests such as swallowing studies, computed tomography (CT), or bronchoscopy.
Infants and young children who have flare-ups of wheezing are given an inhaled bronchodilator (such as albuterol) and, if the wheezing is severe, corticosteroids (such as prednisone) given by mouth or vein.
Children who are unlikely to develop persistent asthma, such as children who do not have signs of allergies or a family history of allergies or asthma and whose episodes of wheezing are relatively mild and infrequent, usually require only inhaled bronchodilators used as needed to control their symptoms.
Most young children with more frequent and/or severe episodes of wheezing are helped by as-needed use of bronchodilators and by daily use of anti-inflammatory drugs that are used for asthma (see Chronic asthma). Although daily use of a leukotriene modifier (such as montelukast or zafirlukast) or a low-dose inhaled corticosteroid (such as beclomethasone) decreases the severity and frequency of episodes of wheezing, these drugs do not change the way the disorder naturally progresses.