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Diagnosing Chronic Cough

It's important to keep in mind that a chronic cough lasts eight weeks or longer because this threshold makes it less likely that the cough is caused by a respiratory infection or common cold. The most important issue is that it has become annoying, frustrating, at times embarrassing and impacting daily quality of life.

Often a chronic cough is a symptom of another disease, such as chronic obstructive pulmonary disease (COPD), asthma or pulmonary fibrosis. If you have one of these diseases and work with your healthcare provider to manage the condition, your cough might improve or go away.

Alternatively, a chronic cough could be a symptom of a lung disease that hasn't yet been diagnosed by your healthcare provider. Your healthcare provider will work with you to take a thorough history and physical exam to attempt to identify the cause of your chronic cough.

It is important to understand that a chronic cough can also be a sign of a disease not related to the lung at all.  Your healthcare provider may have you be evaluated by other specialists besides a lung doctor.  This could include an allergist, an ear, nose and throat specialist (ENT) or an esophagus/stomach specialist.

On rare occasions, a chronic cough cannot be positively linked to another condition or as a side effect of a medication.  This is called idiopathic—or of unknown cause.

Questions about your chronic cough?
Talk with our experts at the American Lung Association Lung HelpLine.  Our service is free and we are here to help you by phone, web chat or email.

When to see your healthcare provider

A cough that lasts less than eight weeks is usually caused by a respiratory infection and will go away on its own.
If you have developed a cough of any kind that goes on for longer than eight weeks, you should see your healthcare provider for a thorough exam to determine what is causing it.   

How Is Chronic Cough Diagnosed?

To identify the cause of your chronic cough, the doctor will ask questions about your medical history, do a physical exam and run some tests.

Medical history

Your doctor will ask you questions about your cough, overall health and activities:

  • When did your cough start?
  • Does your cough bring up mucus?
  • If there is mucus, what's the consistency and color? Is there any blood?
  • Are there any specific triggers to your cough? (weather, air quality, meal times, bedtimes, exposures)
  • Have you been in close contact with anyone who has similar symptoms or a known respiratory infection such as common cold, tuberculosis, pneumonia or whooping cough?
  • Do you have any medical illnesses or chronic diseases?
  • Do you have trouble swallowing?
  • Do you have trouble with indigestion or heartburn?
  • Have you been started on any new medications recently?
  • Have you had any change in your home environment (new carpeting, heating or air conditioning system, new pets, etc.)?
  • Do you have any allergies or experience post nasal drip?
  • What do you do for a living? What's your workplace like? (dusty, damp, cold, etc.)
  • What do you do in your time off? Have you recently traveled?
  • Do you use tobacco products (cigarettes, cigars, pipes or e-cigarettes) or marijuana? Do you use recreational drugs?

Physical exam

At the doctor's office, they will take your vital signs including your temperature. They may check the oxygen level in your blood by attaching a small painless clip to your finger. Your doctor will look at the back of your throat and ears when necessary. They will listen to your lungs and heart with a stethoscope and may also look at your legs and skin.

Diagnostic tests

Your doctor may decide to order tests, which could include:

  • Chest X-ray: Quick and easy chest picture
  • Blood sample: To see if your body is fighting an infection or if there are signs of allergies
  • CT scan of the chest: A better-quality picture of the chest
  • Throat swab: Usually done with a long cotton swab
  • Phlegm or sputum sample: Collected after a deep cough
  • Spirometry: You will be asked to breathe out hard and fast into a small plastic device to measure how well you breathe out air
  • Methacholine challenge test: A breathing test often used to diagnose or rule out asthma

    Page Last Updated: June 24, 2019

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