Croup is a highly contagious upper respiratory viral infection that can affect breathing. It causes swelling of the larynx (voice box) and trachea (windpipe). This causes the airway to narrow, which can get in the way of breathing.

Croup is contagious because the viruses that cause it can be spread through small particles in the air, like when someone coughs or sneezes. You can also get a virus by touching a doorknob or other surface if the virus is on it.

Croup is most common in children 6 months to 3 years old because their windpipes are narrow. As they get older, the airway gets larger, so swelling is less likely to interfere with breathing.

“Adult airways are larger, so we don't typically see croup in adults,” says LaBianca Nona Wright, MD, an internal medicine physician at Northwestern Medicine. “But adults can have a narrow airway because of inflammation, radiation to the chest or a history of smoking.”

Most Common Causes of Croup

For children and adults, a viral infection is the most common cause of croup. They are both susceptible to the same viruses that can lead to croup, including:

• Adenovirus
• Respiratory syncytial virus (RSV)
• Influenza
• Measles
• Parainfluenza

These viruses are common, but many people who have them don’t develop croup.

Croup Symptoms in Children 

Croup is typically mild and starts as a respiratory illness, but symptoms can become severe, and croup can become a life-threatening condition. Symptoms are also usually worse at night for children with croup.

“Kids tend to have more mucus production at night, and when they’re lying down, gravity brings their airway closer together,” says Dr. Wright. “Asthma and acid reflux can also get worse at night, and the temperature change could have an impact on symptoms.”

Symptoms include:

• Seal-barking cough (a loud, harsh cough that sounds like a seal’s bark)
• Hoarse cry or voice
• Stridor (a high-pitched whistling sound when breathing in)
• Raspy breathing
• Runny nose
• Fever

After the first few days of cold-like symptoms, croup can progress into the seal-barking cough.

If your child has croup, you’ll likely want to sleep in the same room with them to monitor their symptoms and sounds when breathing. Children and adults with croup can be contagious for three days after symptoms start, so be sure to wash your hands frequently and avoid sharing cups or utensils to reduce the risk of spreading the virus.

Croup Signs and Symptoms in Adults

Because adults have larger upper airways, croup doesn’t typically affect them the same way. Adults who get croup can have similar symptoms to children, but they can be more serious.

“Adults with croup should seek medical care right away because their symptoms can get worse quickly,” says Dr. Wright. “Many adults with croup can end up in the intensive care unit.”

In children and adults with mild cases who receive prompt medical care, croup symptoms usually improve within a few days; they can recover completely within a week without any long-term effects. For adults, recovery depends on how severe the illness is and the level of medical care required.

Differences Between RSV, Whooping Cough and Croup

RSV

• It’s a viral infection. You can have RSV on its own or RSV and croup at the same time since RSV is one of the viruses that can trigger croup.
• It causes cold-like symptoms, such as sneezing and coughing. Coughing due to RSV can be forceful, and people with RSV can develop wheezing and trouble breathing.
• It can affect people of all ages, but is most serious in infants. “Other than cold-like symptoms, RSV doesn’t typically impact healthy adults the way it would impact a baby younger than 1,” says Dr. Wright.

The key difference is that RSV primarily affects the lower airway, causing wheezing, while croup affects the upper airway, causing the seal-barking cough and stridor.

Whooping cough

• It’s a respiratory infection caused by the bacteria Bordetella pertussis.
• It causes a distinctive cough that sounds like a high-pitched whooping noise.
• It’s not a common cause of croup since it’s caused by a bacteria and not a virus.

Treatment Options for Croup

Treating croup depends on the symptoms. Mild croup in children can usually be treated at home. Adults who think they have croup, even if mild, should seek medical care right away.

Treatments for children include:

• Standing in the bathroom with the door closed and the shower running with hot water (Let your child breathe in the steam.)
• Going outside in the cold air or opening a window (Be sure to bundle up if you go outside with your child.)
• Running a humidifier
• Getting plenty of rest and drinking clear fluids like water
• Over-the-counter medications, such as acetaminophen or ibuprofen (Be sure not to give ibuprofen to a child younger than 6 months old.)
• Placing your child’s head on an elevated pillow if your child is older than 12 months old

If your child is responding to home treatment, you can continue to treat croup at home.

Additional Treatments for Croup

For moderate or severe croup, a healthcare team will typically provide these treatments:

• IV fluids
• Humidified air or oxygen
• Steroids (glucocorticoids)
• Dexamethasone and prednisolone are the most common. One dose by mouth is typically needed, but this medication can also be given as an injection or through an IV. It can reduce airway swelling within six hours.

• Nebulized breathing treatment
• Epinephrine as an inhaled mist can be given every 15 to 20 minutes, and it lasts for about two hours. It can reduce airway swelling within 10 minutes.

When to Seek Medical Care

Although many cases of croup resolve on their own, call 911 or go to the emergency room if you or your child have the following symptoms:

• Trouble taking a deep breath
• Blue-tinged skin
• Chest retractions (the skin around the top of the breastbone and ribs pulls inward when breathing)
• Severe coughing
• Agitated or restless

“There are other conditions with similar symptoms that are life-threatening, such as an abscess in the airway, allergic reaction or certain medications,” says Dr. Wright. “Get an immediate evaluation to have a physical exam if you have one of these medical conditions.”

Can You Get Croup Again?

Recurrent croup is when you have more than two episodes of croup in a year. Croup is not a chronic condition, but if you do have a recurrent case, you may be referred to an otolaryngologist (a physician who specializes in ear, nose and throat conditions) or a pulmonologist (a physician who specializes in lung conditions).

How to Protect Yourself From Croup

Just like with other viral illnesses, you can help prevent croup by reducing your risk of viral infections.

One way to protect yourself is to stay updated on vaccines. There isn't a vaccine for croup, but you can:

• Get your annual flu shot
• Get the RSV vaccine if you’re eligible
• Get a Tdap (whooping cough) booster every 10 years (protects against tetanus, diphtheria and pertussis)

Additional ways to protect yourself from croup:

• Wash your hands regularly.
• Avoid touching your face with your hands.
• Clean surfaces like toys and countertops.
• Avoid contact with people who have symptoms.