Coughing helps protect the lungs from infection, but prolonged inflammation can stimulate nerve reflexes, causing a persistent cough even after a cold has cleared.
For individuals suffering from a cold, once the sneezing, sniffles, and runny nose begin to subside, a common lingering symptom is coughing. The main reason a cough persists is due to residual inflammation, according to Dr. Albert Rizzo, Chief Medical Officer at the American Lung Association. This inflammation can arise from several sources, making it difficult to treat, as reported by Live Science.
Coughing can last for days to weeks after recovering from a cold. (Photo: Medical Republic).
These sources may include viral and bacterial infections that cause inflammation of the airways and nasal passages. This inflammation irritates the mucous membranes in the airways and nose, producing mucus, also known as phlegm and nasal discharge associated with colds. Rhinitis often leads to post-nasal drip, where mucus flows from the nose down the throat. This is a common cause of coughing, according to the National Institutes of Health (NIH). When particles enter the airways through the nose or mouth, they can stimulate receptors in the lungs that send signals to the brain. Pressure builds up in the diaphragm, forcing air out, carrying along dust, food, and mucus.
In addition to rhinitis, a cough that lingers after a cold due to airway inflammation can take several weeks to subside. This duration may be extended if the individual has previously suffered from pneumonia or is a smoker, Rizzo states. When a person is ill, specialized immune cells known as macrophages and neutrophils help combat infections in the airways. These cells also cause inflammation. Occasionally, even after a cold has resolved, such cells remain in the airways, leading to continued inflammation. This is why a cough may persist, explains Dr. Amy Dickey, a pulmonologist and clinical instructor at Massachusetts General Hospital (MGH) and Harvard Medical School.
Meanwhile, the tissue in the airways can be extremely sensitive to particles entering the nose or mouth. This is due to a complex system of nerves and muscles in the airways, throat, and brain that control coughing. “It’s like if you tap a reflex hammer on your knee, your leg will kick out,” Dickey compares. In other words, the virus and mucus act as the reflex hammer, and the cough is akin to the leg kicking out. As inflammation gradually decreases, the reflex becomes less sensitive, and the cough will eventually cease.
Although frequent coughing can be bothersome, coughing serves as an immune function. If irritants and mucus remain in the airways, they can damage tissue or the lungs and even lead to choking. Dickey recommends practicing deep breathing exercises to thin mucus, making it easier to cough it out. This helps eliminate irritants causing inflammation. If a cough persists for more than eight weeks, individuals should seek medical attention for a chest X-ray or to check for signs of lung cancer, emphysema, or other serious conditions.
