Most children with bronchiolitis have mild symptoms and recover within 2 to 3 weeks, but it's important to look out for signs of more serious problems, such as breathing difficulties.

Early symptoms of bronchiolitis tend to appear within a few days of becoming infected.

They're 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

Most cases of bronchiolitis are not serious, but the symptoms can be very worrying.

Symptoms are usually at their worst between day 3 and day 5. The cough usually gets better within 3 weeks.

When to get medical advice

Medical advice is not needed if your child has mild cold-like symptoms and is recovering well. You can usually care for your child at home.

But see your GP or contact NHS 111 if you're worried about your child or they:

• are not feeding normally (they have taken less than half their usual amount during the last 2 or 3 feeds)
• have not had a wet nappy for 12 hours or more
• are breathing very fast
• have a persistent high temperature of 38C or above
• seem very tired or irritable

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

When to call 999

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

Call 999 and ask for an ambulance if:

• your child has difficulty breathing or exhaustion from trying to breathe (you may see the muscles under their ribs sucking in with each breath, they may be grunting with the effort of trying to breathe, or they may be pale and sweaty)
• they're breathing very fast
• you're unable to wake your child or, if woken up, they do not stay awake
• their breathing stops for a long time, or there are regular shorter pauses in their breathing
• their skin turns very pale or blue, or the inside of their lips and tongue are blue (cyanosis)

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

RSV is a very common virus and almost all children are infected with it by the time they're 2 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 when an infected person coughs or sneezes.

Tiny droplets of liquid can be breathed in directly from the air or picked up from a surface they have landed on, such as a toy or table.

For example, your child can become infected after touching a toy that has the virus on it and then touching 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 3 weeks, even after their symptoms have disappeared.

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 breathing difficult.

As babies and young children have small, underdeveloped airways, they're more likely to get bronchiolitis.

Who's most at risk?

Bronchiolitis is very common in infants and is usually mild.

Several things can increase a child's likelihood of developing the infection.

These include:

• being breastfed for less than 2 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're more likely to come into contact with a virus and pass it on

There are also a number of factors that can increase the risk of a child developing more severe bronchiolitis.

These include:

• being under 2 months of age
• having congenital heart disease
• 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)

See 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 may ask if your child has had a runny nose, cough or high temperature and for how long. This will help confirm whether they have the symptoms of bronchiolitis.

They'll listen to your child's breathing using a stethoscope to check 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.

These include:

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

Your GP may recommend that your child is admitted to hospital if they are not feeding properly and are dehydrated, or they're having problems breathing.

Further tests

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

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

These tests might include:

• a mucus sample test (where a sample of mucus from your child's nose will be tested to identify the virus causing their bronchiolitis)
• urine or blood tests
• a pulse oximeter test (where a small electronic device is clipped to your child's finger or toe to measure the oxygen in their blood)

In most cases, bronchiolitis is mild and gets better within 2 to 3 weeks without needing treatment.

A small number of children will still have some symptoms after 4 weeks.

In a few cases, the infection is severe enough to require hospital treatment.

Treatment at home

If you're looking after your child at home, check on them regularly, including throughout the night.

Contact your GP or out-of-hours service if their condition worsens.

Find out when you should call an ambulance

There's no medicine that can kill the virus that causes bronchiolitis, but you should be able to ease mild symptoms and make your child more comfortable.

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 make your child more comfortable while they recover.

Keep your child upright

Keeping your child upright may make it easier for them to breathe, which may help when they're trying to feed.

Make sure your child drinks plenty of fluids

If your child is being breastfed or bottle fed, try giving them smaller feeds more frequently.

Some additional water or fruit juice may stop them becoming dehydrated.

Do not smoke at home

Inhaling smoke from cigarettes or other tobacco products may aggravate your child's symptoms. Avoid smoking 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's upsetting them, you can use paracetamol or ibuprofen, depending on their age.

These are available from pharmacies without a prescription.

Babies and children can be given paracetamol to treat pain or fever if they're over 2 months old.

Ibuprofen may be given to babies aged 3 months or over who weigh at least 5kg (11lbs).

Always follow the manufacturer's instructions when giving your child medication.

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 underdressing them.

Saline nasal drops

Saline (salt water) nasal drops are available from pharmacies without a prescription.

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 are not getting enough oxygen into their blood because they're having difficulty breathing, or if they are not 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 have an underlying health problem. 

Once in hospital, your child will be closely monitored and, depending on the severity of their condition, may have a number of different treatments.

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's attached to your baby's finger or toe. It transmits light through your baby's skin, which the sensor uses 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 has not already been tested, a sample of your child's mucus may be collected and tested to find out which virus is causing the bronchiolitis.

This will confirm whether the respiratory syncytial virus (RSV) is responsible for the infection.

If your child has RSV, they'll need to be kept away from other children in the hospital who are not infected with the virus to stop it spreading.

Feeding

If your child is having trouble feeding, they may be given fluids or milk through a feeding tube (nasogastric tube).

This is a thin plastic tube that goes into your child's mouth or nose and down into their stomach.

If your child cannot use nasogastric fluids or they're at high risk of respiratory failure, they may be given fluids directly into a vein (intravenously).

Nasal suction

Nasal suction is not routinely used in children with bronchiolitis. But it may be recommended if your child's nose is blocked and they're having trouble breathing.

A small plastic tube will be inserted into your child's nostrils to suck out the mucus.

Leaving hospital

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

Your child will be able to leave hospital and return home when their condition has stabilised.

This will be when they have enough oxygen in their blood without the need for further medical assistance, and they're able to take and keep down most of their normal feeds.

Research into other treatments

A number of medicines have been tested to see whether they benefit children with bronchiolitis, but most have been shown to have little or no effect.

For example, antibiotics and corticosteroids are not recommended for treating bronchiolitis. 

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

If your child develops complications from bronchiolitis, it's likely that 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 lung infection called pneumonia. Pneumonia will need to be treated separately.

Contact your GP immediately if any of these complications occur.

In some cases (for example, if your child is having severe breathing difficulties) you'll need to dial 999 and ask for an ambulance so your child can be taken to hospital.

Read more about when to get medical advice and when to call 999.

Who's at risk?

Although serious complications are rare, around 45,000 children with bronchiolitis are admitted to hospital in England each year for further monitoring or treatment.

If your child was born with a health problem, such as a heart or lung condition, there's 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, but it can damage the cells in your child's airways.

This damage can last for 3 to 4 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. But the link is not fully understood.

It's not clear whether having bronchiolitis as an infant increases your risk of developing asthma later in life, 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.

The virus that causes bronchiolitis is very common and easily spread, so it's impossible to completely prevent it.

But you can reduce the likelihood of your child developing or spreading the infection by:

• covering your child's nose and mouth when they cough or sneeze
• using disposable tissues rather than handkerchiefs, and throwing them away as soon as they have been used
• washing your hands and your child's hands frequently, particularly after touching their nose or mouth or after feeding
• asking anyone who comes into contact with your child, such as a relative or nanny, to wash their hands first
• washing and drying eating utensils after use
• 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, particularly during the first 2 months of life or if they were born prematurely (before week 37 of pregnancy)

Stop smoking

Children who inhale smoke passively are at increased risk of developing bronchiolitis.

Do not smoke around your child and do not let other people smoke around them.

Read about giving up smoking.

Preventing bronchiolitis in high-risk children

Children with a high risk of developing severe bronchiolitis may be able to have monthly antibody injections during the winter (November to March).

Children considered to be at high risk include those:

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

The injections may help limit the severity of bronchiolitis if your child becomes infected. But they can be expensive and are not always available on the NHS.

Speak to your GP if you think your child has an increased risk of developing severe bronchiolitis.