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Causes
By Mayo Clinic staffA cough begins when an irritant — stomach acid, mucus, hair spray, perfume, even spicy food — stimulates nerves in your respiratory tract.
An occasional cough is normal — it helps clear foreign substances and secretions from your lungs and prevents infection. But a cough that persists for long periods of time is usually the result of an underlying problem. Examples include:
Postnasal drip
Every day, glands in your nose, sinuses and throat produce mucus, which cleans and moisturizes your nasal passages. Normally, you swallow the fluid without knowing it, but when there's more than usual — from allergies, a cold or sinus infection — you may feel it accumulating in the back of your throat.
This excess mucus, commonly called postnasal drip, can cause irritation and inflammation that trigger your cough reflex. If the postnasal drip is chronic, your cough is likely to become chronic, too. Though postnasal drip is often obvious, it's possible to have the condition without ever having symptoms.
Asthma
This is a common cause of chronic cough in adults and the leading cause in children. Most often, the cough occurs with wheezing and shortness of breath, but in one type of asthma, cough is the only symptom. An asthma-related cough may come and go with the seasons, appear after an upper respiratory tract infection, or become worse when you're exposed to cold air or certain chemicals or fragrances. This type of asthma is frequently referred to as "hyperactive airways disease."
Gastroesophageal reflux disease (GERD)
In this common condition, stomach acid flows back into the tube that connects your stomach and throat (esophagus). The constant irritation in your esophagus, throat and even your lungs can lead to chronic coughing. Acid reflux often causes heartburn and a sour taste, yet close to half the people whose cough is due to reflux have no other symptoms.
Respiratory tract infection
A cough can linger long after most symptoms of a cold, flu, pneumonia or other infection of the upper respiratory tract have gone away. In some cases, this may occur because the infection is lingering. Sometimes, even if the infection is gone, your airways may remain inflamed and therefore especially sensitive to irritants.
Blood pressure drugs
Angiotensin-converting enzyme (ACE) inhibitors, which are commonly prescribed for high blood pressure and heart failure, are known to cause chronic cough in about 20 percent of the people taking them. Most often, the cough begins within a week after starting therapy, but it sometimes may not develop for up to six months. And though the cough usually goes away a few days after the drug is stopped, it can linger for a month or more.
Chronic bronchitis
This long-standing inflammation of your major airways (bronchial tubes) can cause congestion, breathlessness, wheezing and a cough that brings up discolored sputum. Because most people with chronic bronchitis are current or former smokers, the cough is usually a sign of damage to the lungs and airways.
Bronchiectasis
This is a serious, chronic lung condition in which abnormal widening of your bronchial tubes affects their ability to clear mucus from your lungs. It is almost always preceded by pneumonia, although the pneumonia may not be serious enough to prompt a visit to your doctor. Signs and symptoms include a cough that may bring up discolored sputum or blood, shortness of breath and fatigue.
Lung cancer
Only a small percentage of people with a chronic cough have lung cancer, and most are current or former smokers. If you smoke now, smoked at one time or your sputum contains blood, see your doctor.
- Silvestri RC, et al. Evaluation of subacute and chronic cough in adults. http://uptodate.com/home/index.html. Accessed March 9, 2009
- Rosenow EC (expert opinion). Mayo Clinic, Rochester, Minn. March 27, 2009.
- Approach to the patient with a cough. In: Mason RJ, et al. Murray & Nadel's Textbook of Respiratory Medicine. 4th ed. Philadelphia, Pa.: Saunders Elsevier; 2005. http://www.mdconsult.com/das/book/body/124735402-3/813991400/1288/241.html. Accessed March 9, 2009.
- Hill DG. Cough. In: Rakel RE, et al. Conn's Current Therapy. 60th ed. Philadelphia, Pa.: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/124890287-5/814421311/1621/18.html#4-u1.0-B978-1-4160-4435-2..50010-8--cesec4_130. Accessed March 10, 2009.
- Weinberger SE, et al. Treatment of subacute and chronic cough in adults. http://www.uptodate.com/home/index.html. Accessed March 10, 2009.
- Upper endoscopy. National Institute of Diabetes and Digestive and Kidney Diseases. http://digestive.niddk.nih.gov/ddiseases/pubs/upperendoscopy. Accessed March 10, 2009.
- Bronchoscopy. National Heart Lung and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/bron/bron_whatis.html. Accessed March 10, 2009.
- Prednisone. American Society of Health-System Pharmacists. http://www.nlm.nih.gov/medlineplus/druginfo/meds/a601102.html. Accessed March 10, 2009.
- Heartburn, gastroesophageal reflux (GER), and gastroesophageal reflux disease (GERD. National Institute of Diabetes and Digestive and Kidney Diseases. http://digestive.niddk.nih.gov/ddiseases/pubs/gerd. Accessed March 10, 2009.
- Natural medicines in the clinical management of cold and flu: Cough. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed March 10, 2009.
