A barking cough is a loud, hoarse, harsh-sounding cough caused by inflammation or other blockage of the respiratory system, especially in and around the larynx and trachea, that interferes with the normal passage of air. Its name refers to the sound of barking seals, which it resembles. It is most commonly the result of a viral or bacterial infection, but can also be caused by a swallowed object stuck in the airway or by psychological and neuropsychiatric factors. It is best known as one of the symptoms of croup.
Barking cough is one of the most prominent symptoms of croup infections, especially in young children. Croup is a general term that can be applied to similar conditions caused by a variety of of pathogens that can infect the larynx, bronchi, and trachea and interfere with the sufferer's breathing by causing the airway to become swollen. Viral causes of croup include the parainfluenza, influenza, and human respiratory syncytial viruses, while bacterial causes include Corynebacterium diphtheriae, better known as diptheria, Haemophilus influenzae, and Moraxella catarrhalis.
The infection causes the croup sufferer to cough frequently as his or her respiratory system tries to clear itself. The swelling's interference with normal airflow results in the distinctive barking sound. The swelling also causes the croup sufferer's voice to becomes hoarse, and in more severe cases he or she may produce a high-pitched noise while breathing, which is called stridor. Croup is treatable and not usually a serious medical problem, provided it is treated properly, though it can sometimes require hospitalization and in rare cases can be fatal. It is especially dangerous to small children due to their narrower airways.
Other illnesses that cause barking cough are more likely to pose serious health risks. A barking cough can be caused by pertussis, also known as whooping cough, a disease caused by infection with the bacteria Bordetella pertussis. Pertussis causes frequent and severe coughing fits, and the name whooping cough comes from the noise commonly produced by pertussis sufferers as they struggle to draw in air once the fit has stopped. Infection is potentially fatal, especially in children, but is rare in developed countries due to widespread vaccination.
A barking cough occasionally appears as a symptom of epiglottitis, though severe stridor without coughing is more common. Epiglottitis is frequently caused by the same pathogens associated with croup, such as Haemophilus influenzae, and also causes inflammation and constriction of the sufferer's airways. It is considerably more dangerous than croup, however, and can quickly cause fatal respiratory failure within hours of onset unless the sufferer is hospitalized.
Barking cough sometimes occurs for psychological or neurological reasons rather than because of any physical problem in the respiratory system. This is common in people with Tourette's syndrome, who produce involuntary vocalizations that often include coughing. Children who have recovered from a respiratory illness can develop a habit cough that persists after the original reason for the cough is gone.