Bronchiolitis is almost always caused by a viral infection. In the majority of cases the virus responsible is the respiratory syncytial virus (RSV).

RSV is a very common virus. Almost all children are infected with RSV by the time they are two years old. In older children and adults RSV may cause a cough or cold, but in young children it can cause bronchiolitis.

How the infection is spread

Viruses are spread through tiny droplets of liquid from the coughs or sneezes of someone who is infected. The droplets can be breathed in directly from the air or picked up from a surface that they have landed on, such as a toy or table.

For example, your child can become infected if they touch a toy that has the virus on it and then touch their eyes, mouth or nose. RSV can survive on a surface for up to 24 hours.

An infected child can remain infectious for up to three weeks, even after the symptoms have gone.

How it affects the lungs

Once you become infected, the virus enters the respiratory system through the windpipe (trachea). The virus makes its way down to the smallest airways in the lungs (the bronchioles).

The infection causes the bronchioles to become inflamed (swollen) and increases the production of mucus. The mucus and swollen bronchioles can block the airways, making it difficult to breathe. As babies and young children have small, underdeveloped airways, they are more likely to get bronchiolitis.

Who’s most at risk?

Bronchiolitis is very common in infants and is usually mild. However, there are several things that can increase your chances of developing the condition. These include:

• being breastfed for less than two months or not at all
• being exposed to smoke, for example if parents smoke
• having brothers or sisters who attend school or nursery, as they are more likely to come into contact with a virus and pass it on

There are also a number of things that can increase the risk of a child developing more severe bronchiolitis. These include:

• being under two months of age
• having congenital heart disease (a birth defect that affects the heart)
• being born prematurely (before week 37 of pregnancy)
• having chronic lung disease of prematurity (when injury to the lungs causes long-term respiratory problems in premature babies)

If your child develops complications from bronchiolitis, it’s likely they’ll need hospital treatment.

Potential complications of bronchiolitis include:

• cyanosis – a blue tinge to the skin caused by a lack of oxygen
• dehydration – when the normal water content of the body is reduced
• fatigue – extreme tiredness and a lack of energy
• severe respiratory failure – an inability to breathe unaided

In rare cases bronchiolitis can be accompanied by a bacterial infection of the lungs called pneumonia. If this happens, the pneumonia will need to be treated separately.

If any of these complications occur, contact your GP immediately. In some cases you may need to dial 999 for an ambulance to take your child to hospital.

Read more about the symptoms of bronchiolitis for more information about when to seek medical advice.

Who’s at risk?

Although serious complications are rare, around 35,000 children with bronchiolitis are admitted to hospital in England every year for further monitoring or treatment.

If your child was born with a health problem, such as a heart or lung disease, there is an increased risk of complications from bronchiolitis. Their symptoms may be more severe and come on very rapidly. The infection may also make any symptoms of your child’s underlying health problem worse.

Long-term effects of bronchiolitis

Bronchiolitis does not usually cause long-term breathing problems. However, it can cause damage to the cells in your child’s airways. This damage can last for three to four months in some children, causing persistent wheezing and coughing.

Respiratory conditions in later life

There may be a link between bronchiolitis and developing respiratory conditions such as asthma in later life. However, the link is not fully understood.

It is not clear whether having bronchiolitis as an infant makes going on to have asthma more likely, or whether there are environmental or genetic (inherited) factors that cause both bronchiolitis and asthma. 

If your child has repeated bouts of bronchiolitis, their risk of developing asthma later in life may be increased.

Contact your GP if your child has symptoms of bronchiolitis. A diagnosis is usually based on the symptoms and an examination of your child’s breathing.

Your GP will ask about your child’s symptoms – for example, whether they have had a runny nose, cough or high temperature (fever).

They will also listen to your child’s breathing using a stethoscope. Your GP will listen for any crackling or high-pitched wheezing as your child breathes in and out.

If your child has not been feeding very well or has been vomiting, your GP may also look for signs of dehydration to determine whether the water content of their body is reduced.

Signs of dehydration include:

• a dipped fontanelle (the soft spot on the top of the head) in babies
• dry mouth and skin
• drowsiness
• producing little or no urine

Further tests

Further tests for bronchiolitis are not usually necessary. However, some conditions cause similar symptoms to bronchiolitis, such as cystic fibrosis and asthma.

If it is not clear what is causing your child’s symptoms or your child has signs of severe bronchiolitis, your GP may recommend further tests in hospital to confirm the diagnosis.

These tests might include:

• a mucus sample test – a swab is used to collect a sample of mucus from your child’s nose, which is tested to identify virus causing your child’s bronchiolitis
• urine or blood tests
• a pulse oximeter test – this small electronic device is clipped to your child’s finger or toe to measure the oxygen in your child’s blood
• a chest X-ray – this can be used to check for any abnormalities in the lungs, or other conditions such as pneumonia

Bronchiolitis is a common lower respiratory tract infection that most commonly affects babies and young children under a year old.

Most cases are mild and improve without specific treatment within about two weeks, although some children have severe symptoms and need treatment in hospital.

The early symptoms of bronchiolitis are similar to those of a common cold, such as a runny nose and cough.

Further symptoms then usually develop over the next few days, including:

• a slight high temperature (fever)
• a dry and persistent cough
• difficulty feeding
• rapid or noisy breathing 

Read more about the symptoms of bronchiolitis.

When to seek medical help

Although most cases of bronchiolitis aren’t serious, you should contact your GP if:

• you are worried about your baby
• your baby is having some difficulty breathing
• your child has taken less than half the amount that they usually do during the last two or three feeds, or has no wet nappy for 12 hours or more
• your baby has a persistent high temperature
• your baby seems very tired or irritable

Your GP can usually diagnose bronchiolitis based on your child’s symptoms and an examination of their breathing.

You should dial 999 for an ambulance if:

• your baby is having a lot of difficulty breathing and is pale or sweaty
• your baby’s tongue or lips are blue
• there are long pauses in your baby’s breathing

Read more about diagnosing bronchiolitis.

Why it happens

Bronchiolitis is usually caused by a virus known as the respiratory syncytial virus (RSV), which is spread through tiny droplets of liquid from the coughs or sneezes of someone who is infected.

This causes the smallest airways in the lungs (the bronchioles) to become infected and inflamed. The inflammation reduces the amount of air entering the lungs, making it more difficult to breathe.

Read more about the causes of bronchiolitis.

Who is affected?

It is estimated that one in every three children in the UK develop bronchiolitis in their first year of life. The condition is most common in babies between three and six months old. By the age of two, almost all infants have been infected with RSV and up to half of these will have had bronchiolitis.

Bronchiolitis is most common during the winter months, from November to March. It is possible to get bronchiolitis more than once during the same season.

Treating bronchiolitis

There is no medication to kill the viruses that cause bronchiolitis, but the infection usually clears up within two weeks without any need for treatment. Most children can be cared for at home in the same way that you’d treat a cold.

Make sure that your child gets enough fluid to avoid dehydration, and give infants paracetamol or ibuprofen to bring down their temperature if the fever is upsetting them. 

Some babies with bronchiolitis need to go to hospital. This is because they develop more serious symptoms, such as difficulty breathing. This is more common in premature babies (babies born before week 37 of pregnancy) and those born with a heart or lung condition.

Read more about treating bronchiolitis and the complications of bronchiolitis.

Preventing bronchiolitis

Although it is very difficult to prevent bronchiolitis, you can take steps to reduce your child’s risk of catching it and help prevent the virus spreading. This includes:

• washing both your child’s hands and your hands frequently
• washing or wiping toys and surfaces regularly
• keeping infected children at home until their symptoms have improved
• keeping newborn babies away from people with colds or flu
• preventing your child being exposed to tobacco smoke

Some children who are at high risk of severe bronchiolitis may have monthly antibody injections, which help limit the severity of the condition.

Read more about preventing bronchiolitis.

The viruses that cause bronchiolitis are very common and easily spread, so it’s impossible to prevent the condition entirely.

However, the following steps can help you reduce the chances of your child developing or spreading the infection:

• cover your child’s nose and mouth when they cough or sneeze
• use disposable tissues rather than handkerchiefs and throw them away as soon as they have been used
• wash both your child’s hands and your hands frequently, particularly after touching their nose or mouth or after feeding
• ask anyone who comes into contact with your child, such as a relative or nanny, to wash their hands first
• wash and dry eating utensils after use
• wash or wipe toys and surfaces regularly
• keep infected children at home until their symptoms have improved
• keep newborn babies away from people with colds or flu, particularly during the first two months of life or if they were born prematurely (before week 37 of pregnancy)

Stop smoking

Children who inhale smoke passively are more at risk of developing bronchiolitis. If you smoke, avoid doing so around your child or consider stopping smoking.

Preventing bronchiolitis in high-risk children

It may be possible for a child with a high risk of developing severe bronchiolitis to have monthly antibody injections during the winter (November to March). These injections may help limit the severity of the condition if the child becomes infected.

Children who may be considered to be at high risk include:

• those born very prematurely
• those born with a heart or lung condition
• those who have an immune deficiency (a weakened immune system)

However, these injections can be expensive and are not always available on the NHS. Speak to your GP for information and advice if your child is at high risk.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

The information in the Map has been approved by the UK’s leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: bronchiolitis

Most children with bronchiolitis have mild symptoms and recover within two weeks, but it’s important to look out for signs of more serious problems, such as breathing difficulties.

The early symptoms of bronchiolitis tend to appear within a few days of becoming infected. These are usually similar to those of a common cold, such as a blocked or runny nose, a cough and a slightly high temperature (fever).

The symptoms usually get worse during the next few days before gradually improving. During this time your child may develop some of the following symptoms:

• a rasping and persistent dry cough
• rapid or noisy breathing (wheezing)
• brief pauses in their breathing
• feeding less and having fewer wet nappies
• vomiting after feeding
• being irritable

Although most cases of bronchiolitis are not serious, these symptoms can be very worrying.

When to seek medical advice

If your child only has mild cold-like symptoms and is recovering well, there is usually no need to seek medical advice. In these cases you can normally care for your child at home. See treating bronchiolitis for more information about this.

Contact your GP if you are worried about your child, or if your child develops any of the following symptoms:

• struggling to breathe
• poor feeding (your child has taken less than half the amount that they usually do during the last two or three feeds)
• no wet nappy for 12 hours or more
• a breathing rate of 50-60 breaths a minute
• a high temperature of 38°C (100.4°F) or above
• seeming very tired or irritable

It is particularly important to seek medical advice if your baby is under 12 weeks old or they have an underlying health problem, such as a congenital (present from birth) heart or lung condition.

When to call 999

While it is unusual for children to need hospital treatment for bronchiolitis, the symptoms can get worse very quickly.

Call 999 for an ambulance if:

• your child has severe breathing difficulties or exhaustion from trying to breathe – you may see the muscles under your child’s ribs sucking in with each breath, your child may be grunting with the effort of trying to breathe, or they may be pale and sweaty
• your child has a rapid breathing rate of more than 60 breaths a minute
• you are unable to rouse (wake) your child or, if roused, they do not stay awake
• your child’s breathing stops for a long period (more than 10 seconds at a time), or there are regular shorter pauses in breathing of 5-10 seconds
• your child’s skin begins to turn very pale or blue, or the inside of their lips and tongue are a blue colour (known as cyanosis)

In most cases bronchiolitis is mild and gets better without any specific treatment within about two weeks.

A small number of children will still have some symptoms after four weeks, and in a few cases the condition is severe enough to require treatment in hospital.

Treatment at home

If you’re looking after your child at home, check on them regularly, including throughout the night. If their condition worsens, contact your GP.

Read more about the symptoms of bronchiolitis for advice about when to call an ambulance.

There is no medicine that can kill the viruses that cause bronchiolitis. However, you should be able to ease mild symptoms and make your child more comfortable by following the advice below.

To avoid the infection spreading to other children, take your child out of nursery or day care and keep them at home until their symptoms have improved.

The following advice may help your child feel more comfortable while they recover.

Keep your child upright

This may help make their breathing easier and may be useful when they are trying to feed. If your child has a nap in an upright position, make sure that their head does not fall forward by supporting it with something, such as a rolled-up blanket.

Drink plenty of fluids

If your child is being breastfed or bottlefed, try giving them smaller feeds more frequently. Some additional water or fruit juice may help avoid dehydration.

Keep the air moist

If you have access to an air humidifier, using it to moisten the air may help to ease your child’s cough.

Your home should be heated to a comfortable temperature, but do not make it too warm as this will dry out the air.

Keep a smoke-free environment

Inhaling smoke from cigarettes or other tobacco products may aggravate your child’s symptoms. If you smoke, avoid doing so around your child.

Passive smoking can affect the lining of your child’s airways, making them less resistant to infection. Keeping smoke away from your child may also help prevent future episodes of bronchiolitis.

Relieving a fever

If your child has a high temperature (fever) that is upsetting them, you can consider using paracetamol or ibuprofen, depending on their age. These are available over the counter from pharmacies without prescription.

Babies and children can be given paracetamol to treat fever or pain if they are over the age of two months. Ibuprofen may be given to children who are three months old or over and weigh at least 5kg (11lbs).

Always follow the manufacturer’s instructions and do not give aspirin to children under the age of 16.

Do not try to reduce your child’s high temperature by sponging them with cold water or under-dressing them.

Saline nasal drops

Saline (salt water) nasal drops are available over the counter from pharmacies. Placing a couple of drops of saline inside your child’s nose before they feed may help to relieve a blocked nose.

Always follow the manufacturer’s instructions or check with your pharmacist before using saline nasal drops.

Treatment in hospital

Some children with bronchiolitis need to be admitted to hospital. This is usually necessary if they aren’t getting enough oxygen into their blood because they are having difficulty breathing, or if they aren’t eating or drinking enough.

Children are more at risk of being admitted to hospital if they were born prematurely (before week 37 of pregnancy) or with an underlying health problem. 

Once in hospital, your child will be monitored and treated in a number of ways, as explained below.

Extra oxygen

The level of oxygen in your child’s blood will be measured with a pulse oximeter. This is a small clip or peg that is attached to your baby’s finger or toe. It transmits light through your baby’s skin and the sensor uses this to detect how much oxygen is in their blood.

If your child needs more oxygen, it can be given to them through thin tubes in their nose or a mask that goes over their face.

If it hasn’t already been tested, at this point a sample of your child’s mucus may be tested to see which virus is causing the bronchiolitis. This will confirm whether the respiratory syncytial virus (RSV) is responsible for the condition.

If your child has RSV, they will need to be kept away from other children in the hospital who are not infected with the virus. This is to control the spread of the virus.

Read more about how bronchiolitis is diagnosed.

Feeding

If your child is having trouble feeding, they may be given fluids or milk through a feeding tube. This is a thin plastic tube that goes into your child’s mouth or nose and down into their stomach. Alternatively, they may be given fluids intravenously (directly into a vein).

Nasal suction

If your child’s nose is blocked and they have trouble breathing, nasal suction may be used. This involves a small plastic tube being inserted into their nostrils to clear out the mucus.

Leaving hospital

Most children who are admitted to hospital will need to stay there for a few days.

Your child will be discharged from hospital and can go home when they have enough oxygen in their blood without the need for medical assistance, and they are able to take and keep down most of their normal feeds.

Research into other treatments

Several medicines have been tested to determine whether they benefit children with bronchiolitis, and most have been shown to have little or no effect.

Research also suggests that chest physiotherapy, where physical movements or breathing techniques are used to relieve the symptoms, is of no benefit.