Croup: Symptoms, causes, and treatment

Croup is an inflammation of the larynx and trachea, mostly seen in young children. A barking cough, varying degrees of airway obstruction, and hoarseness are the defining symptoms.

A range of infectious conditions can lead to croup. It is also known as laryngotracheobronchitis.

The barking cough that is characteristic of croup results from swelling and inflammation around the vocal chords and windpipe. Symptoms normally improve within a few days, but hospitalization may be needed in severe cases.

Croup affects 3 percent of children between 6 months and 3 years of age in the United States.

Fast facts on croup

Croup is an infection of the larynx and trachea, occurring mostly in children.

It is characterized by a barking cough and can be caused by either viruses and bacteria.

There 17 stages for grading the severity of croup.

Symptoms will normally self-resolve. One dose of a corticosteroid drug called dexamethasone can help prevent the return of symptoms.

What is croup?

Croup is categorized either by the cause or the specific symptoms that accompany the cough.

Viral croup

Child coughs into elbow
Croup is recognizable by its distinctive barking cough.

Viral croup is the most common type.

Acute croup is most often caused by a virus, as is recurrent, or spasmodic, croup. They have a similar presentation, making it difficult to distinguish between the two for diagnosis.

Some researchers argue that spasmodic croup may be linked to allergens such as pollen or a bee sting, or that it may be an allergic reaction to viral antigens, rather than a direct result of a viral infection.

Bacterial croup

Bacterial croup is caused by a bacterial infection. This type is much rarer than viral croup and can be divided into bacterial tracheitis, laryngotracheobronchitis (LTB), laryngotracheobronchopneumonitis (LTBP), and laryngeal diphtheria.

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Croup can have several causes.

Viral croup

Respiratory syncytial virus
Respiratory syncytial virus is one of the causes of viral croup.

Types 1, 2, and 3 of the human parainfluenza virus account for 80 percent of all cases of croup.

Human parainfluenza virus 1 (HPIV-1) is the most common cause of croup, with types 1 and 2 causing 66 percent of infections. Type 4 has been associated with milder illness but is not well understood.

The following viruses cause the remaining cases of croup:

respiratory syncytial virus


influenzas A and B




Viral infection typically takes the following course to develop into croup:

The virus infects the nose and throat.

The virus spreads along the back of the throat to the larynx and trachea.

As the infection progresses, the top part of the trachea becomes swollen.

The space available for air to enter the lungs becomes narrower.

Children compensate for this by breathing more quickly and deeply, leading to croup symptoms.

The child may become restless or anxious as breathing becomes more difficult. This agitation can also narrow the throat, increase breathing difficulties and worsening the agitation.

The effort required to breathe faster and harder is tiring, and, in severe cases, the child may become exhausted and unable to breathe on their own.

Croup also has genetic indications. Both spasmodic croup and acute croup are more common in children with a family history of croup. The risk of spasmodic croup may also be increased by a previous attack.

Bacterial croup

Bacterial infection usually affects the same areas as a viral infection but is typically more severe and requires different treatment.

Most instances of bacterial croup, more commonly called bacterial tracheitis, are due to secondary bacterial infection from Staphylococcus aureus (S. aureus). Other bacteria that cause croup include S. pyogenes, S. pneumonia,Haemophilus influenza, and Moraxella catarrhalis.

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