Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link




The Manual's Editorial Staff

Reviewed/Revised Sep 2023
Get the full details

What is croup?

Croup is swelling in the windpipe and voice box. It’s caused by a viral infection and is most common in children ages 6 months to 3 years.

  • Children with croup have a cough that sounds like a seal barking

  • Children may make a loud squeaking noise when breathing in (stridor) and have a fever and runny nose

  • Most children get better at home in 3 to 4 days, but some need to be hospitalized

Call your child’s doctor right away if your child has trouble breathing.

When should my child see a doctor for croup?

Call your child’s doctor right away if your child has any of these warning signs:

  • Trouble breathing

  • Fast heartbeat

  • Blue lips or fingers (from low oxygen in the blood)

  • Unusual tiredness

What causes croup?

Croup is caused by several different viruses. Your child can get croup any time of year, but croup is less common in the summer.

What are the symptoms of croup?

Symptoms of croup are often worse at night and may even wake your child up.

At first, your child has cold symptoms such as:

  • Runny nose

  • Sneezing

  • Slight coughing

  • Slight fever (100° to 101° F or 37.8° to 38.3° C )

Later, your child may have:

  • Frequent cough that sounds like a seal barking

After 3 to 4 days, the cough may change to sound more like a normal cough.

With severe croup, your child may also have:

  • Trouble breathing

  • A loud squeaking sound when breathing in (stridor)

  • Sometimes, a blue color around the lips from low oxygen levels in the blood

How do doctors tell if my child has croup?

Doctors can usually tell if your child has croup based on the child’s symptoms, especially the barking sound of the cough. Doctors will:

  • Sometimes, do x-rays of your child’s neck and chest

How do doctors treat croup?

For mild croup, doctors will treat your child at home with:

  • Rest

  • Clear fluids such as water or juice

  • Cool-mist humidifier to moisten the air

To help ease coughing, try one of the following:

  • Run a hot shower in your bathroom to create steam your child can breathe

  • Take your child outside to breathe cold night air

  • Have your child breathe cold air from the open freezer

Most children with mild croup will feel better in 3 to 4 days.

If your child has trouble breathing, go to the hospital's emergency department right away. There, doctors will give your child fluids by vein and medicines such as:

  • A corticosteroid by mouth or in a shot

  • Epinephrine through a nebulizer

A nebulizer is an electric or battery-powered machine that turns liquid medicine into a fine spray that you child can easily breathe in through a face mask.

If your child's symptoms get better, doctors may send your child home.

If your child still has trouble breathing, doctors will keep your child in the hospital. Usually doctors will continue to:

  • Measure the oxygen level in your child’s blood by placing a sensor on the finger (pulse oximetry)

  • Give extra oxygen through a face mask if your child’s oxygen level is too low

  • Continue giving medicines by nebulizer and by vein

Drugs Mentioned In This Article

Generic Name Select Brand Names
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
quiz link

Test your knowledge

Take a Quiz!