Childhood Diseases

Updated 27 March 2018

What is croup?

Croup is an acute viral inflammation of the upper and lower respiratory tracts.


Alternative name: Laryngo-tracheo bronchitis or LTB

Croup is an acute, viral inflammation of the upper and lower respiratory tract.

It mainly involves the:

• Larynx – the “voice box” containing the vocal chords.

• Trachea – the windpipe.

• Bronchi – the large airways leading to the lungs.

• Bronchioles – the small airways in the lungs.

• Lung tissue.

The main symptoms are caused by swelling and inflammatory secretions in the larynx, the area immediately around the vocal chords. This obstruction results in difficult breathing, especially during inhalation (when breathing air in). 

Croup most often occurs in children, and the laboured breathing usually tires the child very much.

In very severe cases, the lungs are unable to work efficiently in moving oxygen into the blood, with the result that the child may become depleted of oxygen.

Croup is characterised by inspiratory stridor (a harsh, crowing sound when inhaling air), subglottic swelling (swelling below the vocal chords), and respiratory distress that’s most pronounced during inspiration.

Acute epiglottitis is a condition that should always be considered when children present with croup. Here a bacterial infection caused by bacteria known as Haemophilus influenzae results in acute swelling of the epiglottis, the small flap of tissue at the back of the throat that guards the airway entrance to the lungs.

This can rapidly lead to upper airway obstruction. If the diagnosis isn’t made promptly, the child is at serious risk of dying.

In many developed countries, according to the World Health Organization (WHO), croup is caused by parainfluenza or influenza virus. Bacterial infection is rarely the cause.

Reviewed by paediatrician Prof Eugene Weinberg. MBChB; FCP (SA); PAED (SA). March 2018.


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