What makes you cough
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Understanding the Causes and Mechanisms of Cough
Coughing is a common reflex action that serves to clear the airways of irritants and secretions. It can be triggered by a variety of factors, ranging from infections to environmental irritants. This article synthesizes the current research on what makes you cough, focusing on the common cold, chronic cough, and the underlying mechanisms.
Common Cold and Acute Cough
Viral Infections and Upper Airway Irritation
The common cold is the most frequent cause of acute cough. Viral infections of the upper respiratory tract, such as those caused by rhinoviruses, lead to direct irritation of the upper airway structures, resulting in cough . This irritation often produces a condition known as rhinosinusitis, which can further exacerbate coughing.
Postinfectious Cough and Inflammatory Response
In some cases, the cough persists even after the resolution of the initial infection. This "postinfectious" cough is likely due to an inflammatory response triggered by the viral infection, leading to a condition known as upper airway cough syndrome (UACS), previously referred to as postnasal drip syndrome.
Chronic Cough: Common Causes
Upper Airway Cough Syndrome (UACS)
UACS, often resulting from rhinosinus conditions, is a prevalent cause of chronic cough. It involves the continuous irritation of the upper airways, leading to persistent coughing .
Asthma and Nonasthmatic Eosinophilic Bronchitis (NAEB)
Asthma and NAEB are significant contributors to chronic cough. These conditions involve inflammation and hypersensitivity of the airways, which can trigger a persistent cough .
Gastroesophageal Reflux Disease (GERD)
GERD is another common cause of chronic cough. The reflux of stomach acids into the esophagus can irritate the airway and trigger coughing. This condition often coexists with other causes of chronic cough, such as UACS and asthma, forming a "pathogenic triad" .
Environmental and Occupational Factors
Exposure to Irritants
Chronic cough can also result from exposure to environmental pollutants, such as cigarette smoke and particulate matter. Occupational exposures to irritants can similarly lead to persistent coughing, either as an isolated symptom or as part of a more significant disease process .
Allergic and Nonallergic Triggers
Both allergic reactions and nonallergic environmental triggers, such as tobacco and marijuana smoke, can contribute to chronic cough. These triggers can cause inflammation and irritation of the airways, leading to persistent coughing.
Mechanisms of Cough
Sensory Nerve Activation
Coughing is primarily triggered by the activation of sensory receptors in the airways. These receptors, including those in the larynx and lower respiratory tract, send impulses to the brainstem, initiating the cough reflex . The release of neuropeptides, such as substance P, from C-fibres in the vagus nerve plays a crucial role in this process.
Neurogenic Inflammation
Neurogenic inflammation, caused by the activation of C-fibre receptors, can lead to the release of sensory neuropeptides, which further stimulate cough receptors. This complex interaction between peripheral and central nervous systems modulates the sensitivity and pattern of the cough reflex .
Role of Gastroesophageal Reflux
Reflux events can increase the rate of coughing by irritating the airway. This is particularly evident in patients with idiopathic chronic cough, where reflux and phonation (voice production) are significant triggers.
Conclusion
Coughing is a multifaceted reflex that can be triggered by a variety of factors, including viral infections, chronic conditions like asthma and GERD, and environmental irritants. Understanding the underlying mechanisms, such as sensory nerve activation and neurogenic inflammation, is crucial for effective diagnosis and treatment. By addressing both the primary causes and the pathways involved, healthcare providers can better manage and alleviate chronic cough.
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