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About Bronchiolitis

Bronchiolitis is a common illness of the respiratory tract. It's caused by an infection that affects the tiny airways, called the bronchioles, that lead to the lungs. As these airways become inflamed, they swell and fill with mucus, which can make breathing difficult.


  • most often affects infants and young children because their noses and small airways can become blocked more easily than those of older kids or adults
  • typically happens during the first 2 years of life, most commonly at about 3 to 6 months of age
  • is more common in males, premature babies, children who have not been breastfed, and those who live in crowded conditions

Bronchiolitis is usually caused by a viral infection, most commonly respiratory syncytial virus (RSV). RSV infections are responsible for more than half of all cases of bronchiolitis. Other viruses associated with bronchiolitis include rhinovirus (the common cold virus), influenza (flu), human metapneumovirus, adenovirus, coronavirus, and parainfluenza. Childcare attendance and exposure to cigarette smoke also can increase a child's risk for bronchiolitis.

Although it's often a mild illness, some babies are at risk for severe bronchiolitis — including those who were born prematurely, have a chronic heart or lung disease, or have a weakened immune system due to illness or medicines. Those infants need to be treated in a hospital.

Kids who have had bronchiolitis might be more likely to develop asthma later in life. It's not yet clear whether the illness causes or triggers asthma, or whether kids who eventually develop asthma were just more prone to developing bronchiolitis as infants. Experts continue to study the relationship between bronchiolitis and the later development of asthma.

Signs and Symptoms

The first symptoms of bronchiolitis are usually the same as those of a common cold:

  • stuff nose and congestion
  • runny nose
  • cough
  • fever

These symptoms last a day or two and are followed by worsening of the cough and wheezing (high-pitched whistling noises when exhaling).

Sometimes, more severe respiratory difficulties gradually develop. Signs to watch for include:

  • fast, shallow breathing
  • a rapid heartbeat
  • retractions — when the areas below the ribs, between the ribs, and in the neck sink in as a child inhales
  • flaring of the nostrils
  • irritability, with difficulty sleeping and signs of fatigue (tiredness) or lethargy
  • vomiting after coughing
  • poor appetite or not feeding well, causing decreased peeing and fewer wet diapers

Sometimes these symptoms can lead to dehydration. Less commonly, babies (especially preemies) may have episodes where they briefly stop breathing (called apnea) before developing other symptoms.

In severe cases, symptoms may worsen quickly. A child with severe bronchiolitis may get very tired from the work of breathing and have poor air movement in and out of the lungs due to the clogging of the small airways. The skin can turn blue (called cyanosis), which is especially noticeable in the lips and fingernails.


The infections that cause bronchiolitis are contagious. The germs can spread in tiny drops of fluid from an infected person's nose and mouth, which may become airborne via sneezes, coughs, or laughs, and also can end up on things the person has touched, such as used tissues or toys.

Infants in childcare centers have a higher risk of getting an infection that may lead to bronchiolitis because they're in close contact with lots of other young children.


The best way to prevent the spread of viruses that can cause bronchiolitis is washing hands well and often. It may help to keep infants away from others who have colds or coughs. Babies who are exposed to cigarette smoke are more likely to develop severe bronchiolitis compared with those from smoke-free homes. So it's important to protect children from secondhand smoke.

There's no bronchiolitis vaccine available yet, but a medication can be given to ease the severity of the disease. It's recommended only for infants at high risk of severe disease, such as those born very prematurely or those with chronic lung or heart disease. The medicine, which contains antibodies to RSV, is given as an injection monthly during peak RSV season.


The incubation period (the time between infection and the onset of symptoms) ranges from several days to a week, depending on the infection causing the bronchiolitis.


Cases of bronchiolitis usually last about 12 days, but kids with severe cases can cough and have wheezing for weeks. The illness generally reaches its peak on the second or third day after coughing begins, causing breathing difficulty before slowly getting better.

Professional Treatment

Fortunately, most cases of bronchiolitis are mild and don't need specific professional treatment. Antibiotics aren't useful because bronchiolitis is caused by a viral infection, and antibiotics are only effective against bacterial infections. Medicine may sometimes be given to help open a child's airways.

Infants who have trouble breathing, are dehydrated, or appear fatigued should be checked by a doctor. Those who are moderately or severely ill may need to be hospitalized, watched closely, and given fluids and humidified oxygen. Rarely, in very severe cases, some babies are placed on respirators to help them breathe until they start to get better.

Home Treatment

The best treatment for most kids is time to recover and plenty of fluids. Making sure a child drinks enough fluids can be tricky, though, because infants with bronchiolitis may not feel like drinking. They should be offered fluids in small amounts often.

Indoor air, especially during winter, can dry out airways and make the mucus stickier. Some parents use a cool-mist vaporizer or humidifier in the child's room to help loosen mucus in the airway and relieve cough and congestion. If you use one, clean it daily with household bleach to prevent mold build-up. Avoid hot-water and steam humidifiers, which can be hazardous and can cause scalding.

To clear nasal congestion, try a bulb syringe and saline (saltwater) nose drops. This can be especially helpful just before feeding and sleeping. Sometimes, keeping a child in a slightly upright position may help ease labored breathing.

Acetaminophen can be given to reduce fever and make your child more comfortable. Be sure to give the appropriate dose based on your child's weight.

When to Call the Doctor

Call your doctor if your child:

  • is breathing quickly, especially if this is accompanied by retractions or wheezing
  • might be dehydrated due to vomiting or a poor appetite
  • is sleepier than usual
  • has a high fever
  • has a cough that gets worse
  • appears very tired or lethargic

Get immediate help if you feel your child is having difficulty breathing and the cough, retractions, or wheezing are getting worse, or if his or her lips or fingernails appear blue.

Reviewed by: Irina S. Ten, MD
Date reviewed: October 2015

Related Resources

OrganizationNational Heart, Lung, and Blood Institute (NHLBI) The NHLBI provides the public with educational resources relating to the treatment of heart, blood vessel, lung, and blood diseases as well as sleep disorders.
OrganizationCenters for Disease Control and Prevention (CDC) The CDC (the national public health institute of the United States) promotes health and quality of life by preventing and controlling disease, injury, and disability.
OrganizationAmerican Lung Association The mission of this group is to prevent lung disease and promote lung health. Contact the group at: American Lung Association
61 Broadway, 6th Floor
NY, NY 10006
(212) 315-8700
OrganizationAmerican Academy of Pediatrics (AAP) The AAP is committed to the health and well-being of infants, adolescents, and young adults. The website offers news articles and tips on health for families.
OrganizationAmerican Academy of Family Physicians This site, operated by the American Academy of Family Physicians (AAFP), provides information on family physicians and health care, a directory of family physicians, and resources on health conditions.

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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