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Causes of Cough

Causes of Cough

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Updated June 03, 2014

What are the Causes of a Chronic Cough?

A cough lasting for more than 8 weeks is termed a chronic cough. Some people can experience a chronic cough for years, and treatment may not be successful. For these people, a referral to an allergist or pulmonologist (a physician who specializes in the lungs) should be made, as expert medical care may be needed.

The most common causes of a chronic cough include:

  • Post-nasal drip (phlegm draining from the back of the nose into the throat)
  • Asthma (and cough-variant asthma)
  • Gastroesophageal reflux disease (GERD)
  • Eosinophilic bronchitis
  • Medication induced (ACE inhibitors)
  • Smoking

Many experts recommend performing a chest X-ray and a cat scan of the sinuses as part of the evaluation for a chronic cough. Specialists (allergists and pulmonologists) will also perform specialized tests for asthma. When a chest X-ray is normal, then the above causes account for the overwhelming majority of cases of chronic coughing.

The physician will perform a history and physical examination, which may give clues to the cause of the chronic cough. In some instances, it may be necessary to give trials of treatment for the above, as the physical examination may not give clues to the cause of the cough.

Irritants and medications. People who smoke or who are exposed to irritants in a job or hobby should avoid these triggers. Medications such as ACE inhibitors (blood pressure medications such as lisinopril and many others, with the generic names all ending in “pril”) are well-known causes of coughing, and should be switched by the physician to a different type of medication. A cough may last for up to 4 weeks after an ACE inhibitor is stopped.

Post-nasal drip. This is the most common cause of chronic cough. Post-nasal drip, if present on the history (throat-clearing) or on the physical exam, may be treated with a decongestant/anti-histamine combination (as above in acute cough) and a prescription nasal spray (such as a nasal steroid). If these medications do not help, it may be necessary to ensure that the post-nasal drip is not due to a sinus infection by performing a sinus cat scan.

Asthma. Asthma is the second most common cause of chronic cough. A cough may be the only sign of asthma, although many people will also complain of wheezing and shortness of breath as well. Special tests, including spirometry and bronchoprovocation studies, can help determine if the cough is due to asthma. However, these tests may be normal, so a trial of asthma therapy (such as an inhaled steroid) may be needed for approximately 1-2 months.

GERD. GERD is the third most common cause of chronic cough, and the majority of people with this type of cough do not realize that they have GERD. Another form of GERD, called laryngopharyngeal reflux (LPR), causes a cough with a hoarse voice and throat clearing. Specialized testing can be performed for GERD and LPR, but in the types that cause a cough, these may be expensive and uncomfortable. A trial of therapy for GERD and LPR (the treatment is typically the same), typically for many weeks to months, may be needed for the cough to resolve.

Eosinophilic bronchitis. This form of chronic cough occurs in up to 13 percent of people, and can be diagnosed with looking at the person’s sputum (phlegm) under a microscope. Because there is no other testing available to diagnose this type of cough, a trial of inhaled steroids (for 1-2 months) is often part of the therapies given to a person with a chronic cough when the cause is not readily apparent.

If the cough persists despite the above, referral to a specialist (allergist or pulmonologist) may be required for further evaluation. Less common causes of chronic cough include habit cough (nervous tic), ear wax (or other foreign body) impaction in the ear, Tourette’s syndrome, bronchiectasis, various types of lung cancers, heart failure, interstitial lung diseases, etc.

Sources:

Irwin RS, Madison JM. The Diagnosis and Treatment of Cough. N Engl J Med. 2000; 343: 1715-21.

Weldon DR. Differential Diagnosis of Chronic Cough. Allergy and Asthma Proc. 2005; 26: 345-51.

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