Cough

The complications of coughing can be classified as either acute or chronic. Acute complications include cough syncope (fainting spells due to decreased blood flow to the brain when coughs are prolonged and forceful), insomnia, cough-induced vomiting, subconjunctival hemorrhage or "red eye", coughing defecation and in women with a prolapsed uterus, cough urination. Chronic complications are common and include abdominal or pelvic hernias, fatigue fractures of lower ribs and costochondritis. Chronic or violent coughing can contribute to damage to the pelvic floor and a possible cystocele.[3]

A cough can be the result of a respiratory tract infection such as the common cold, COVID-19, acute bronchitis, pneumonia, pertussis, or tuberculosis. In the vast majority of cases, acute coughs, i.e. coughs shorter than 3 weeks, are due to the common cold.[5] In people with a normal chest X-ray, tuberculosis is a rare finding. Pertussis is increasingly being recognised as a cause of troublesome coughing in adults.

After a respiratory tract infection has cleared, the person may be left with a postinfectious cough. This typically is a dry, non-productive cough that produces no phlegm. Symptoms may include a tightness in the chest, and a tickle in the throat. This cough may often persist for weeks after an illness. The cause of the cough may be inflammation similar to that observed in repetitive stress disorders such as carpal tunnel syndrome. The repetition of coughing produces inflammation which produces discomfort, which in turn produces more coughing.[6] Postinfectious cough typically does not respond to conventional cough treatments. Treatment consists of any anti-inflammatory medicine (such as ipratropium)[6] to treat the inflammation, and a cough suppressant to reduce frequency of the cough until inflammation clears.[7] Inflammation may increase sensitivity to other existing issues such as allergies, and treatment of other causes of coughs (such as use of an air purifier or allergy medicines) may help speed recovery.[8]

When coughing is the only complaint of a person who meets the criteria for asthma (bronchial hyperresponsiveness and reversibility), this is termed cough-variant asthma. Atopic cough and eosinophilic bronchitis are related conditions. Atopic cough occurs in individuals with a family history of atopy (an allergic condition), abundant eosinophils in the sputum, but with normal airway function and responsiveness. Eosinophilic bronchitis is characterized by eosinophils in sputum and in bronchoalveolar lavage fluid without airway hyperresponsiveness or an atopic background.[9] This condition responds to treatment with corticosteroids. Cough can also worsen in an acute exacerbation of chronic obstructive pulmonary disease.

Asthma is a common cause of chronic cough in adults and children. Coughing may be the only symptom the person has from their asthma, or asthma symptoms may also include wheezing, shortness of breath, and a tight feeling in their chest. Depending on how severe the asthma is, it can be treated with bronchodilators (medicine which causes the airways to open up) or inhaled steroids. Treatment of the asthma should make the cough go away.

Chronic bronchitis is defined clinically as a persistent cough that produces sputum (phlegm) and mucus, for at least three months in two consecutive years. Chronic bronchitis is often the cause of "smoker's cough". The tobacco smoke causes inflammation, secretion of mucus into the airway, and difficulty clearing that mucus out of the airways. Coughing helps clear those secretions out. May be treated by quitting smoking. May also be caused by pneumoconiosis and long-term fume inhalation.

In people with unexplained cough, gastroesophageal reflux disease should be considered.[4] This occurs when acidic contents of the stomach come back up into the esophagus. Symptoms usually associated with GERD include heartburn, sour taste in the mouth, or a feeling of acid reflux in the chest, although, more than half of the people with cough from GERD don't have any other symptoms. An esophageal pH monitor can confirm the diagnosis of GERD. Sometimes GERD can complicate respiratory ailments related to cough, such as asthma or bronchitis. The treatment involves anti-acid medications and lifestyle changes with surgery indicated in cases not manageable with conservative measures.

Coughing may be caused by air pollution including tobacco smoke, particulate matter, irritant gases, and dampness in a home.[4] The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, the individual's health status and genetics. People who exercise outdoors on hot, smoggy days, for example, increase their exposure to pollutants in the air.

A foreign body can sometimes be suspected, for example if the cough started suddenly when the patient was eating. Rarely, sutures left behind inside the airway branches can cause coughing. A cough can be triggered by dryness from mouth breathing or recurrent aspiration of food into the windpipe in people with swallowing difficulties.[10][11]

ACE inhibitors are drugs often used to treat high blood pressure that can sometimes be the cause of a cough as a side effect, and stopping their use will stop the cough.[12]

A tic cough, previously called a habit cough, is one that responds to behavioral or psychiatric therapy after organic causes have been excluded. Absence of the cough during sleep is common, but not diagnostic. A tic cough is thought to be more common in children than in adults.[13] A similar disorder is the somatic cough syndrome previously called the psychogenic cough.

Some cases of chronic cough may be attributed to a sensory neuropathic disorder.[14] Treatment for neurogenic cough may include the use of certain neuralgia medications. Coughing may occur in tic disorders such as Tourette syndrome, although it should be distinguished from throat-clearing in this disorder.

Cough may also be caused by conditions affecting the lung tissue such as bronchiectasis, cystic fibrosis, interstitial lung diseases and sarcoidosis. Coughing can also be triggered by benign or malignant lung tumors or mediastinal masses. Through irritation of the nerve, diseases of the external auditory canal (wax, for example) can also cause cough. Cardiovascular diseases associated with cough are heart failure, pulmonary infarction and aortic aneurysm. Nocturnal cough is associated with heart failure, as the heart does not compensate for the increased volume shift to the pulmonary circulation, in turn causing pulmonary edema and resultant cough.[15] Other causes of nocturnal cough include asthma, post-nasal drip and gastroesophageal reflux disease (GERD).[16] Another cause of cough occurring preferentially in supine position is recurrent aspiration.[15]

Given its irritant nature to mammal tissues, capsaicin is widely used to determine the cough threshold and as a tussive stimulant in clinical research of cough suppressants. Capsaicin is what makes chili peppers spicy, and might explain why workers in factories with these fruits can develop a cough.

Coughing may also be used for social reasons, and as such is not always involuntary. A voluntary cough, often written as "ahem", can be used to attract attention or express displeasure, as a form of nonverbal, paralingual metacommunication.[17][18]

Coughing, and huffing are important ways of removing mucus as sputum in many conditions such as cystic fibrosis, and chronic bronchitis.

A cough can be classified by its duration, character, quality, and timing.[4] The duration can be either acute (of sudden onset) if it is present less than three weeks, subacute if it is present between three or eight weeks, and chronic when lasting longer than eight weeks.[4] A cough can be non-productive (dry) or productive (when phlegm is produced that may be coughed up as sputum). It may occur only at night (then called nocturnal cough), during both night and day, or just during the day.[4]

A number of characteristic coughs exist. While these have not been found to be diagnostically useful in adults, they are of use in children.[4] A barky cough is part of the common presentation of croup.[21] A staccato cough has been classically described with neonatal chlamydial pneumonia.[22]