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  • A respiratory infection that causes a barking cough and hoarseness
  • Symptoms include a barking cough, hoarseness, fever, difficulty breathing
  • Treatment includes at-home treatment, over-the-counter medications, steroids, epinephrine, oxygen
  • Involves infectious diseases, pediatrics, pediatric infectious diseases



When an infant or child has a persistent cough that sounds like a barking seal, they may have croup, a common childhood upper respiratory infection. Children with croup experience inflammation in the windpipe (trachea), voice box (larynx), and/or bronchi (the airways within the lungs connected to the windpipe). The inflammation typically causes children to make croup-specific “barking” sounds while they cough or breathe.

About 3% of children in the United States are diagnosed with croup each year. The condition is slightly more common among boys than girls. Most cases are mild, although some children need to be treated in the hospital. Among children aged 5 and younger, croup accounts for about 7% of hospitalizations nationwide. Most infants and children recover completely from croup within 3 to 7 days.

Certain childhood vaccinations help to reduce the risk of croup because they protect against conditions that may cause serious illness. Infants and children should receive vaccines for measles, diphtheria, and Haemophilus influenzae (Hib) at the recommended ages to protect against those diseases, as well as croup.

What is croup?

Croup is a respiratory system infection that affects infants and young children. It’s often caused by a virus.

Children with croup can have some symptoms of a cold or the flu, but what characterizes this condition is a cough with a distinctive sound. A croup cough sounds like a barking seal, and a child with croup often makes involuntary high-pitched whistling noises when they inhale. These unusual-sounding noises occur because the windpipe and/or bronchial airways have become inflamed. This swelling makes it harder for the child to breathe easily.

Mild croup can be successfully treated at home with over-the-counter medication and home remedies. However, moderate and severe croup should be evaluated and treated by a doctor.

What causes croup?

Croup is usually caused by a viral infection. Less commonly, however, it can be caused by a bacterial infection.

Viruses that can cause croup include:

  • Parainfluenza virus (the most common cause)
  • Flu (influenza virus)
  • RSV (respiratory syncytial virus)
  • Coronaviruses, including SARS-CoV-2, the virus that causes COVID-19
  • Rhinovirus
  • Enterovirus
  • Adenovirus
  • Human bocavirus
  • Human metapneumonovirus
  • Measles

Except for Mycoplasma pneumoniae, which can cause a minor illness similar to croup, bacterial infections are rarely the cause of croup. Other bacterial infections, including by Haemophilus influenzae type b (known as Hib) and Cornebacterium diptheriae (the cause of diphtheria), can cause croup, but they are exceedingly rare in the United States due to vaccines.

Bacterial infections can also occur as a complication or secondary infection in people who have viral croup.

What are the symptoms of croup?

Infants and children who have croup often experience:

  • Coughing that sounds like a barking seal
  • Sneezing
  • Runny nose
  • Congestion
  • Low-grade fever
  • Hoarseness
  • A high-pitched whistling noise when the child inhales (stridor)
  • Difficulty breathing
  • Retraction (sinking in) of the chest when inhaling
  • Bluish lips

It’s common for croup symptoms to become worse in the evening and overnight. Sometimes, difficulty breathing or other symptoms can awaken a child from sleep. Symptoms typically improve in the morning and worsen again in the evening.

What are the risk factors for croup?

Infants and children may be at increased risk of croup if they:

  • Are under 5 years of age
  • Are male
  • Have had croup before

Croup is more prevalent in the fall and winter than in the spring and summer, like many other viruses. Therefore, infants and children may be more likely to get croup during colder months of the year.

How is croup diagnosed?

Because there are telltale sounds associated with croup, your child may be diagnosed after a doctor listens to the cough and learns about their medical history. Your child should also receive a physical exam, and may require diagnostic tests to confirm the diagnosis or rule out other conditions.

When you’re asked to share details about your child’s medical history, tell your pediatrician about your child’s symptoms, including details about a barking cough or breathing difficulties. You may be asked if your child has had croup before or if the condition runs in the family.

During a physical exam, if your child has a cough that sounds like a seal’s bark and/or if they make high-pitched whistling sounds when they inhale, they may be diagnosed with croup. Other noteworthy signs include lips that look blue, as well as, on inhalation, nostrils that flare or a chest that that retracts (sinks in).

Sometimes, croup is diagnosed after a physical exam and medical history. Other times, diagnostic tests are recommended, such as a chest and neck X-ray. Doctors may be able to see a swollen or narrowed trachea on an X-ray, but this step isn’t necessary much of the time. An X-ray can also help doctors rule out other causes, such as a swallowed object that is blocking airflow in the trachea.

How is croup treated?

Treatments for croup vary, depending on whether it’s mild, moderate, or severe.

For mild croup, you may care for a child at home. Make sure your child drinks plenty of fluids to stay hydrated. Keeping your child calm is also important because crying can make it more difficult for them to breathe easily.

When a child has mild croup, some parents put a humidifier in their bedroom or run a hot shower so the child can sit in the bathroom to breathe in the steamy mist. Other parents take their child outside at night to breathe in cool air. While these treatments shouldn’t be harmful, they also aren’t proven by research to be helpful.

It’s important to note that over-the-counter cough and cold medications should not be given to a child with croup.

Moderate and severe croup requires medical attention. Doctors may prescribe:

  • Dexamethasone, a corticosteroid. This treatment can resolve a child’s symptoms more quickly and shorten the duration of illness. In certain cases, other corticosteroids may be used.
  • Epinephrine, a medication that is often given for life-threatening allergic reactions. When a child has severe croup and breathing is extremely difficult, epinephrine helps to open the airways. It’s typically nebulized (turned into a mist), so that a child may inhale the medication.
  • Dexamethasone plus epinephrine. For severe cases, doctors may prescribe both drugs.
  • Oxygen, to help patients breathe more easily.
  • Neuraminidase inhibitors, such as Tamiflu, but only when croup is caused by flu.
  • Antibiotics, but only in rare cases when croup is caused by bacteria, not a virus. Antibiotics may also be used if a child has a bacterial infection in addition to having viral croup.
  • Intubation, in very rare cases, when a child is unable to breathe unassisted.

What is the outlook for infants and children with croup?

In most cases, croup resolves completely within a week, although some children may be sick for longer periods.

Some infants and children get croup more than once, although this is not common.

Sometimes, croup may become life-threatening if a child’s airway becomes severely blocked. Prompt medical intervention should help, and the child should completely recover.

This article was medically reviewed by Carlos Oliveira, MD, PhD.