I saw 17 patients in my primary care practice yesterday. Six of them were coughing.

One of the most basic parts of my job is sorting out who’s a little sick from who’s very sick, or in danger of getting very sick. How do I do that when so many people have the same symptom? And, as a patient, how do you know when your own cough is worth a trip to the doctor (especially when it’s cold, you feel rotten, and the waiting room is likely to be full of … coughing people)?

First, what is a cough? One way to think of it is as a version of speaking or singing: air is being expelled through the throat in such a way that a noise comes out. In coughing, however, the expulsion of air is caused by some irritant, is reflexive and involuntary (though you can fake a cough, usually unconvincingly) and occurs against closed vocal cords, producing a distinctive sound. Some coughing sounds–the “bark” of croup (listen here) and the “whoop” of whooping cough (listen here) — are especially distinctive.

Dozens of conditions can cause a cough. The most common ones I see in adults are:

• viral upper respiratory infections
• influenza (“the flu”)
• bacterial pneumonia and bronchitis
• asthma
• allergies
• congestive heart failure
• gastroesophageal reflux (“GERD”)
• chronic obstructive pulmonary disease (“COPD”)
• smoking
• lung cancer
• post nasal drip
• medication side effects — especially from the blood pressure medications known as ACE inhibitors (lisinopril, Accupril, Monopril, etc.).

Some of the clues I use to sort through these are the quality of the cough (wet or dry, throaty or deep, etc.); timing (acute vs. chronic); accompanying symptoms (wheezing, fever, etc.); and characteristics of the patient (age, medical history, exposure to smoke, medications, or sick contacts, allergens, etc.)

Someone taking lisinopril who feels well other than a tickly feeling in their throat that’s been making them cough for weeks is easy to diagnose, as is someone who’s got a high fever, body aches, chills, and a kid at home with the flu, or someone who coughs every time they eat a heavy meal and then lies down in bed and gets heartburn (the acid irritates the throat).

Things get tricky when the variables scramble and combine a smoker with GERD who takes lisinopril and has a sick kid at home, for example. When that happens–and it often does–you work your way through the list of possible diagnoses (“the differential”) and eliminate them one by one, starting with the most serious and the most likely the way a detective considers crime suspects. The physical exam, blood tests, a sputum sample, a chest X-ray, and a consultation with a specialist may all be helpful in sorting through the list. Sometimes, a “therapeutic trial” is the key to the diagnosis: if changing the blood pressure medication, treating the GERD, or having the patient avoid cats cures the cough, you have your answer.

This time of year, the vast majority of coughs I see are due to upper respiratory viral infections. Each of the six coughing patients I saw yesterday had one, I determined. I advised them to rest, drink soothing liquids, use over the counter cough medications as needed, cough into their elbows and stay out of work or school if they have fevers or until they felt better (yes, a subjective call).

There are symptoms that may signal a cough that may require more treatment and evaluation than this. These include:

• fever >101
• shortness of breath
• wheezing
• coughing up blood
• chest pain
• cough that lasts more than several days
• exposure to the flu, whooping cough, or other infectious diseases

Even these symptoms don’t necessarily mean the cough is serious. I’m seeing plenty of people this year with fevers and coughs lasting two and even three weeks or more who still turn out to have simple viral infections. But these are symptoms that are worth a call or even a trip to your doctor’s office.

Please don’t be offended when we hand you a mask at the door.

Suzanne Koven is an internal medicine physician who blogs at In Practice at Boston.com, where this article originally appeared. She is the author of Say Hello To A Better Body: Weight Loss and Fitness For Women Over 50. 

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