What can cause a persistent dry cough?

Q. I have developed a dry cough that has persisted for almost two months. I otherwise feel fine. I have never smoked. What might cause this?

A. My first question is whether you had cold symptoms or COVID before the cough began. If so, it's common to still have a cough for weeks after an upper respiratory infection. However, when someone has a cough lasting six weeks or longer, my practice is to order a chest x-ray to check for an underlying lung problem.

A virus causes most upper respiratory infections. After the infection is long gone, inflamed tissues and hypersensitive nerves remain in the larynx (voice box), trachea (windpipe), or bronchi (airways). These changes can last for much longer than people realize. In addition to a nagging cough, many people also develop wheezing.

In these cases, I usually prescribe an albuterol inhaler (Proventil, Ventolin, generic versions) to use as needed. Adults can take up to two puffs every four to six hours. If this does not control the cough, sometimes an inhaler that contains a corticosteroid can be added.

Coughing also can be a side effect of medications, particularly ACE inhibitors, such as lisinopril (Prinivil, Zestril, others) or enalapril (Vasotec), that are used to treat high blood pressure and heart disease. The other common causes of a persistent cough in a nonsmoker with clear lungs and a normal chest x-ray are postnasal drip, acid reflux, and undiagnosed asthma.

Sometimes people don't have typical symptoms associated with these conditions. For example, a person might not have nasal congestion yet still have postnasal drip. Acid reflux can cause a cough without heart-burn. And sometimes people with asthma don't notice wheezing.

When there are no clues to the possible cause of a chronic cough, I often first recommend a decongestant, with or without an antihistamine, to treat possible postnasal drip. If that doesn't help, my next advice addresses the possibility of acid reflux, including

• not lying down for three hours after eating
• eating smaller meals
• noting which foods make the symptoms worse and avoiding them
• taking a short course of a proton-pump inhibitor like omeprazole (Prilosec).

If these approaches don't help, additional diagnostic tests may be needed. These could include breathing tests to detect undiagnosed asthma or checking for acid in the upper esophagus.

Many over-the-counter cold products claim to reduce cough. If you try a cough suppressant, look for one that contains the ingredient dextromethorphan. While clinical study results are mixed, most studies suggest it decreases cough compared with a placebo.

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