What causes a cough
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Causes of Cough: An Overview
Coughing is a common reflex action that helps clear the airways of irritants and mucus. It can be caused by a variety of factors, ranging from infections to environmental irritants. This article synthesizes the findings from multiple research studies to provide a comprehensive overview of the causes of cough.
Acute Cough: Common Cold and Respiratory Infections
Viral Infections and Common Cold
The most frequent cause of acute cough is the common cold, which is typically triggered by viral infections. These infections cause direct irritation of the upper airway structures, leading to cough . The inflammation and irritation from the viral infection can also result in rhinosinusitis, further contributing to the cough .
Postinfectious Cough
In some cases, a cough can persist even after the initial infection has resolved. This "postinfectious" cough is often due to an inflammatory response triggered by the viral infection, which can lead to a subacute or chronic cough if not treated .
Chronic Cough: Underlying Conditions
Upper Airway Cough Syndrome (UACS)
Previously known as postnasal drip syndrome, UACS is a common cause of chronic cough. It is often associated with rhinosinus conditions and can be clinically silent apart from the cough itself Pratter2006Chung2008.
Asthma and Nonasthmatic Eosinophilic Bronchitis (NAEB)
Asthma is a well-known cause of chronic cough, characterized by airway inflammation and hyperreactivity. NAEB, which presents with similar symptoms but without the typical asthma features, is another significant cause Pratter2006Palombini1999.
Gastroesophageal Reflux Disease (GERD)
GERD is another major contributor to chronic cough. The reflux of stomach acids into the esophagus can irritate the airway, leading to a persistent cough Pratter2006Palombini1999.
Environmental and Occupational Factors
Exposure to environmental pollutants, such as cigarette smoke, cooking fumes, and allergens like dust mites and fungi, can also cause chronic cough. Occupational exposures to irritants and allergens can lead to conditions like hypersensitivity pneumonitis and occupational asthma, which are associated with chronic cough Tarlo2006Tarlo2016.
Specific Conditions: Whooping Cough and Exercise-Induced Cough
Whooping Cough (Pertussis)
Whooping cough, caused by the bacterium Bordetella pertussis, is characterized by severe coughing fits. Research has identified bacterial factors such as pertussis toxin and lipooligosaccharide that induce the production of bradykinin, a known cough inducer, exacerbating the cough response .
Exercise-Induced Cough
Athletes often experience cough related to exercise, which can be due to asthma, exercise-induced bronchoconstriction, or environmental exposures during training. This type of cough is typically assessed using bronchoprovocation tests and treated based on the underlying cause .
Mechanisms of Cough
Sensory and Motor Nerve Involvement
Coughing involves both sensory and motor nerves. Irritants stimulate receptors in the vagus nerve, leading to the release of neuropeptides like substance P, which triggers the cough reflex. This reflex involves the closing and opening of the vocal cords, resulting in the characteristic sound of a cough .
Chronic Cough Pathophysiology
Chronic cough can lead to plastic changes in the brainstem and airway nerves, enhancing the cough reflex. Structural and inflammatory changes in the airway mucosa can either cause or result from repetitive coughing, making the condition self-perpetuating .
Conclusion
Cough can be caused by a wide range of factors, from common viral infections to chronic conditions like asthma and GERD. Environmental and occupational exposures also play a significant role. Understanding the underlying cause is crucial for effective treatment and management. Further research is needed to explore the mechanisms and develop targeted therapies for different types of cough.
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