Coughing helps protect the lungs from infection, but prolonged inflammation can trigger nerve reflexes that cause a lingering cough long after the cold is gone.
Coughing can last for days to weeks after a cold has cleared up. Photo: Medical Republic
For people with colds, after the sneezing, sniffling, and runny nose subside, one symptom that often lingers is a cough. The main reason a cough doesn't go away is residual inflammation, said Dr. Albert Rizzo, chief medical officer at the American Lung Association. This inflammation can come from several sources, making it difficult to treat, according to Live Science .
These sources can include viral and bacterial infections that cause inflammation of the airways and nose. This inflammation irritates the lining of the airways and nose, producing mucus, the phlegm and runny nose associated with colds. Rhinitis often leads to postnasal drip, which is mucus that drains from the nose into the throat. This is a common cause of cough, according to the National Institutes of Health . When particles enter the airways through the nose or mouth, they can trigger receptors in the lungs that tell the brain. Pressure then builds up in the diaphragm and air is forced out, carrying dust, food, and mucus with it.
In addition to rhinitis, a cough that lasts after a cold is caused by airway inflammation and can take several weeks to subside. This can take longer if the person has had pneumonia or smokes, Rizzo says. When a person is sick, special immune cells called macrophages and neutrophils help fight infection in the airways. Those cells also cause inflammation. Sometimes, after a cold is over, such cells stay behind, causing the airways to become inflamed. That’s why the cough can persist, says Amy Dickey, MD, a pulmonologist and clinical nurse at Massachusetts General Hospital (MGH) and an instructor at Harvard Medical School.
Meanwhile, the tissue in your airways can be extremely sensitive to particles that enter your nose or mouth. That’s because there’s a complex system of nerves and muscles in your airways, throat, and brain that control your cough. “It’s like if you hit your knee with a reflex hammer, your leg will extend,” Dickey says. In other words, viruses and mucus are the reflex hammer, and coughs are like the leg extending. As inflammation subsides, the reflex becomes less sensitive, and the cough goes away.
Although coughing can be uncomfortable, it serves as an immune function. If irritants and mucus get stuck in the airways, they can damage tissue or the lungs, even causing suffocation. Dickey recommends practicing deep breathing to loosen mucus and make it easier to cough up. This will help clear the irritants that are causing inflammation. If the cough lasts longer than eight weeks, the person should see a doctor for a chest X-ray or to check for signs of lung cancer, emphysema, or other serious conditions.
An Khang (According to Live Science )
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