Introduction

A baby who has bronchiolitis may become breathless and wheezy. Some babies need hospital care. But most young children who have bronchiolitis aren't seriously ill and recover within a week at home.

We've brought together the best research about bronchiolitis and weighed up the evidence about how to treat it. You can use our information to talk to your doctor and decide which treatments are best for your child.

Bronchiolitis is an infection of the small tubes (bronchioles) inside the lungs. The infection is usually caused by a virus and often affects children under 2 years.

Air normally enters the lungs through the windpipe, down larger branching tubes (known as bronchi) and then into the smallest tubes (bronchioles).

The air passes from the bronchioles into millions of tiny air sacs (alveoli) in the lung and then into the bloodstream.

A child with bronchiolitis has inflamed bronchioles.^[1] The bronchioles become swollen and full of mucus. This makes it harder for oxygen to reach the lungs and get into the bloodstream. Your child may wheeze and breathe faster to try to get the air they need.

Bronchiolitis is caused by a virus. Respiratory syncytial virus (RSV) is the most common type. It causes bronchiolitis in 7 in 10 children with the illness. In winter, nearly all bronchiolitis is caused by this virus.

RSV is also a common cause of colds, and usually causes only mild symptoms in adults. It's spread in the air by coughing and sneezing. By the age of 2 years, almost all children have had an infection caused by RSV.^[2]

For most children, an RSV infection isn't serious. But in about 1 in 5 babies and young children, the virus can infect the airways lower down and cause bronchiolitis.

In early spring, a virus called parainfluenza virus type 3 is often the cause.^[3] This virus also causes croup. Croup is when a child's voice box or windpipe becomes inflamed. The child usually has a 'barking' cough.

The symptoms of bronchiolitis aren't severe for most young children. Your child probably won't need to go to hospital. But the illness can become serious for babies and infants who have other lung diseases or heart diseases.

You can't easily prevent your baby getting bronchiolitis. The viruses that cause it are common and all around us. There's no vaccine available yet to protect your baby against RSV.

But if you have a cold, you can try to stop the virus from spreading. You should wash your hands often, especially before you pick up or touch your child.

Why does my child have bronchiolitis?

Some things make it more likely that your child will get bronchiolitis. They include being:^[4]

• Six months of age or younger

• Born prematurely (before 37 weeks in the pregnancy)

• Exposed to cigarette smoke (including in the womb)^[5]

• In crowded living conditions

• Bottle-fed rather than breast-fed

• Born with Down's syndrome.^[6]

Your child is more likely to get bronchiolitis severely if they:^[7]

• Have close contact with other infected children

• Have a heart disease from birth

• Have a long-term lung disease

• Were born prematurely

• Had a low birth weight^[5]

• Did not start breastfeeding in hospital^[5]

• Have low oxygen levels because of any of the conditions above

• Have difficulty fighting infections (an immune problem)

• Are less than 6 weeks old.