The Medicine Cabinet: A Lingering Cough Should Be Checked by Doctor

The Medicine Cabinet: A Lingering Cough Should Be Checked by Doctor

Q: I have been coughing for almost six weeks for no obvious reason. I have never smoked and haven’t been sick with a cold or the flu. What makes you cough and why would it linger?

A: The cough is a vital player in the body’s defense against disease. Coughing expels mucus, microbes and foreign particles from the respiratory tract, protecting the lungs from infection and inflammation.

The cough begins with an initial gasp that draws air deep into the lungs. Next, the glottis snaps shut, putting a lid over the trachea, or windpipe. The third step is the forceful contraction of the muscles of the chest cage, abdomen and diaphragm. In normal breathing, these muscles push air gently from the lungs up through the nose and mouth. But when the glottis is closed, the air can’t move out, so tremendous pressure builds up in the air passages. Finally, the glottis swings open and the air rushes out.

A cough can be a conscious, voluntary act if you feel like something is caught in your throat, or it can be an uncontrollable, involuntary reflex. In the latter case, stimulation of nerves in the larynx (“voice box”) and respiratory tract initiates the entire process. These nerves can be irritated by infections, allergies, cold air, tumors, chemical agents such as smoke, mechanical factors such as dust particles, or by normal body fluids such as nasal mucus or stomach acid.

It’s no wonder, then, that so many different things can trigger a cough.

While persistent coughing is common and usually not due to anything serious, I recommend a visit to your doctor. You doctor will examine you, listen to your lungs and often order an X-ray, especially if you are a present or past smoker.

Smoking is the leading cause of a chronic cough. But a lingering cough is also a worry for nonsmokers. Fortunately, benign problems are responsible for most chronic coughs in nonsmokers.

Dozens of conditions can cause a recurrent, lingering cough, but the lion’s share are caused by just five: postnasal drip, asthma, acid reflux, chronic bronchitis and treatment with ACE inhibitors, used for high blood pressure. Many people have several of these conditions, but in nonsmokers, the first three, singly or in combination, account for nearly all chronic coughs.

Don’t be frustrated if it takes time for you and your doctor to find out what’s causing your cough. Often the exam and chest X-ray don’t provide the answer. For example, you could have asthma without wheezing or not be aware that you have postnasal drip or acid reflux. That means a trial of some different treatments or some additional testing.

Howard LeWine, M.D. is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School.
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