What Causes Croup?

little girl coughing

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  • A viral infection is considered to be the most common cause of croup, usually the parainfluenza I virus
  • Children or babies can develop croup when they inhale respiratory droplets that are either coughed or sneezed out by infected people from their surroundings

Croup occurs when there is swelling around the larynx (vocal cords), trachea (windpipes) and bronchi (bronchial tubes) found in the lungs and throat, and when the passageway surrounding these body parts is narrowed.1 Once a cough forces air through this passage, the vocal cords make a distinctive coughing sound similar to a barking seal. A high-pitched whistling sound, or stridor, is also produced when the patient takes a breath.

How Viruses Can Increase the Risk of Croup

A viral infection is considered to be the most common cause of croup, usually the parainfluenza I virus.2 Other parainfluenza viruses that can trigger croup are parainfluenza II, parainfluenza III and parainfluenza IV. In some cases, croup may also occur because of other viruses such as:3

Influenza A and B (flu viruses)

Measles virus

Rhinovirus (common cold virus)

Enteroviruses

Respiratory syncytial virus (RSV) that can lead to severe breathing problems and pneumonia in babies

Other Possible Causes of Croup

Apart from these viruses, an infant or child may also develop croup because of the following:4,5

Inhaling a foreign object like a peanut or pen cap

Epiglottitis, wherein there's an inflammation of the epiglottis, or the flap at the base of the tongue that prevents food from going into the windpipe

Tracheitis, an inflammation of the trachea or windpipe

Inhaling irritants like chemicals

Abnormality in the airway that's present since birth

Acid reflux, wherein acid leaks back out of the stomach and into the throat

Abscess in the tissues at the back of the throat

Angioedema or a swelling of the skin's deeper layers

A congenital lesion

Allergic reactions to substances like pollen or dust mites

Risk Factors for Croup

A child’s risk of a croup infection goes up between 6 months and 3 years of age, with peak incidence of the disease occurring once the child turns 2 years old.6 In some cases, however, babies as young as 3 months or children up to 15 years old can have croup.7 Adults may have croup too, although this is very rare.8

Croup tends to affect more boys than girls, and is typically prevalent from October to March,9 or at least during the late autumn and early winter months.10 This is probably because more viruses like colds and flu are in the air during this period.11

How Do Children or Babies Get Croup?

Children or babies can develop croup from their surroundings when they inhale respiratory droplets that are either coughed or sneezed out by infected people. Contact with toys or surfaces that harbor these contaminated droplets can also put a child or baby at risk for this disease. An infection may arise if a child or a baby touches a contaminated surface and then touches his or her eyes, nose or mouth.12

MORE ABOUT CROUP

Croup: Introduction

What Is Croup?

Is Croup Contagious?

Croup in Adults

Croup Symptoms

Croup Causes

Types of Croup

Croup Treatment

Essential Oils for Croup

Croup Prevention

Croup FAQ


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