What triggers coughing
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Triggers of Cough: An In-Depth Analysis
Environmental Irritants and Chronic Cough
Common Environmental Triggers
Environmental irritants are significant contributors to chronic cough. A comprehensive review identified 214 different triggers, including pollutants, allergens, and occupational exposures, which can induce chronic cough across various regions globally. Common environmental triggers include poor air quality, changes in air temperature, and exposure to tobacco and marijuana smoke . These irritants can cause both acute and chronic cough, with long-term exposure potentially leading to persistent coughing.
Occupational Exposures
Occupational environments also play a crucial role in chronic cough. Exposure to dust, chemicals, and other irritants in the workplace can lead to cough as an isolated symptom or as part of a more significant disease process. The need for systematic assessment of these factors is emphasized to better understand and manage occupationally induced chronic cough.
Pathophysiology of Cough Triggers
Sensory Nerve Activation
Coughing is primarily triggered by the activation of sensory nerves in the airways. Inhaled irritants stimulate receptors in unmyelinated C-fibres of the vagus nerve, leading to the release of neuropeptides such as substance P, which plays a pivotal role in initiating the cough reflex. This process involves both sensory and motor nerves, with the sudden opening of vocal cords during increased intrathoracic pressure producing the characteristic sound of a cough.
Inflammatory and Infectious Pathways
Inflammation and infection are also key pathways in cough induction. Respiratory pathogens and inflammatory mediators can directly interact with sensory nerve receptors, triggering a cough response. This mechanism not only helps clear the airways but also facilitates the transmission of infectious diseases through cough-generated aerosols.
Specific Triggers and Their Associations
Asthma and Airway Sensitivity
In patients with asthma, certain triggers such as cold air and stress are more likely to induce coughing. These patients often exhibit higher sensitivity to inhaled methacholine and elevated levels of exhaled nitric oxide (NO), indicating increased airway sensitivity. Additionally, allergen exposure can heighten cough reflex sensitivity, as seen in asthmatic patients exposed to capsaicin following allergen challenge.
Gastroesophageal Reflux (GER)
GER is another significant trigger for chronic cough. Triggers like spices and meals are more frequently reported by patients with GER-related cough, highlighting the role of acid reflux in stimulating cough receptors.
Neuronal Hypersensitivity
Patients with refractory chronic cough often report triggers such as throat tickle and irritation, which are consistent with neuronal hypersensitivity. This hypersensitivity can make the cough response more unpredictable and challenging to manage .
Conclusion
Cough can be triggered by a wide range of environmental, occupational, and physiological factors. Understanding these triggers and their underlying mechanisms is crucial for effective diagnosis and management. Environmental irritants, occupational exposures, and specific conditions like asthma and GER play significant roles in chronic cough. Further research and systematic assessment are needed to bridge the gap in understanding and managing these triggers effectively.
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