Common Causes of a Persistent Cough

A persistent cough—a cough that lasts eight weeks or longer—can be a sign of asthma, allergies, or a chest infection. Also known as a chronic, lingering, or nagging cough, a persistent cough can interfere with sleep and affect your quality of life.

A persistent cough is usually caused by something mild and easily treatable. In rare cases, though, it can indicate a serious underlying lung or heart condition. Whether it's a dry cough or a productive cough with mucus (sputum), a cough that lingers should be evaluated by a healthcare provider.

This article explores common and uncommon causes of persistent cough in adults and children. It also explains how the cause of a persistent cough is diagnosed.

Common Causes

A persistent cough is often caused by something that is not serious and relatively easy to treat. The following are the most common causes of persistent coughs in adults.

Postnasal Drip

Postnasal drip from hay fever (allergic rhinitis), sinus infections, nasal polyps, or other conditions is the most common cause of a chronic cough. These are referred to as upper airway conditions.

Seasonal allergic rhinitis comes and goes with a seasonal pattern, and year-round causes of allergies might not have a consistent pattern.

Asthma

Asthma can cause persistent and intermittent coughing, and it usually also causes other symptoms, such as wheezing and shortness of breath. These symptoms generally will occur together when asthma is flaring up.

Cough-variant asthma is a type of asthma where cough is the most noticeable symptom.

Acid Reflux

Gastroesophageal reflux disease (GERD) can cause a chronic cough. Some people don't have typical symptoms such as heartburn, and the only symptom may be a chronic cough.

Cough due to GERD is usually worse at night after lying down in bed.

Eosinophilic Bronchitis

Eosinophilic bronchitis is one of the top four causes of chronic cough in adults. It is caused by an immune cell reaction.

The diagnosis can be somewhat challenging because lung function tests are usually normal. The condition usually responds to inhaled steroids.

Common Causes in Children

The most common causes of a cough are not the same for children and adults. Common causes of chronic cough in a very young child can include:

• Asthma
• Prolonged episode of bacterial bronchitis
• Upper airway cough syndrome, a post-infectious cough, can sometimes linger for many weeks following an upper respiratory infection

Less Common Causes

These are less common, but not rare, causes of a chronic cough:

• Smoker's cough is a very common cause of a persistent cough.
  
• Worldwide, tuberculosis is a common cause of chronic cough.
• ACE inhibitors can cause a dry cough. Examples of these medications include Vasotec (enalapril) and Zestril (lisinopril).
• Chronic bronchitis is a form of chronic obstructive pulmonary disease (COPD) that often affects people who smoke and can also be related to environmental exposures and other factors.
• Whooping cough (pertussis) is not very common due to immunization. This infection can affect people who are not immunized or people who are immunized and develop a weak immune system.

Uncommon Causes

There are many other less common conditions that can cause a cough. Some of these can be life-threatening and may worsen if they aren't diagnosed and treated quickly.

Examples of uncommon causes of a persistent cough include;

• Lung cancer: For only 2% of people with a persistent cough, lung cancer is the underlying cause. And roughly 57% of people who have lung cancer have a cough. Characteristics of a cough related to lung cancer can be difficult to distinguish from a cough due to other causes.
• Tumors in or near the lungs: A chronic cough may occur due to other tumors in the chest, such as lymphomas. A persistent cough may also occur due to lung metastases from other cancers such as breast cancer, colon cancer, bladder cancer, and prostate cancer.
• Lung diseases: These include emphysema, bronchiectasis, and sarcoidosis.
• Fungal infections: These include coccidioidomycosis and histoplasmosis.
• Sarcoidosis: Sarcoidosis is a disease in which granulomas form throughout the body, including the lungs. It usually causes a dry cough.
• Inhaling a foreign object: This can lead to an ongoing cough and subsequent infection.
• Heart failure: Fluid build-up in the lungs caused by heart failure can lead to persistent coughing or wheezing with blood-tinged mucus.
  

Diagnosis

It is important to make an appointment with your doctor if you have a cough that persists.

Questions you may be asked at your medical visit may include:

• How long have you been coughing? 
• Has the cough been worsening?
• Is the cough steady or does it come and go?
• Is it worse after meals or is it worse at night?
• Is the cough dry, or have you been coughing up phlegm (mucus)?
• Have you coughed up blood?
• What other symptoms have you been experiencing? For example, fever, shortness of breath, allergy symptoms, wheezing, or unexplained weight loss?
• What other medical problems do you have?
• Has anyone in your family had similar symptoms? Do you have a family history of bronchitis, asthma, emphysema, or lung cancer?
• Do you, or have you ever, smoked?
• Have you been exposed to secondhand smoke?
• What medications are you taking (including herbal supplements)?
• Have you recently traveled?

Tests to Evaluate a Persistent Cough

Depending on the severity of your cough, your healthcare professional will give you treatment to control your symptoms and make you feel more comfortable. They may also recommend tests to determine the cause.

Blood tests may be done to look for any evidence of infection.

You may have a chest X-ray or a chest computerized tomography (CT) scan. If you have symptoms of sinusitis, a CT scan of your sinuses may be recommended.

Other tests that may be recommended include:

• Allergy tests
• Pulmonary function tests to screen for changes that occur with asthma and emphysema
• Esophageal pH testing to test for acid reflux as a possible cause of a persistent cough is an uncommon test
• Bronchoscopy to check for foreign bodies or evaluate your airways for a tumor if imaging of the chest shows findings that look like a tumor
• Laryngoscopy to examine your throat and voice box

Summary

A persistent cough should be evaluated by a healthcare provider. The most common causes of an ongoing cough are not serious and include post-nasal drip, asthma, acid reflux, and eosinophilic bronchitis.

Less commonly, a persistent cough may be caused by tuberculosis, whooping cough, or COPD. It can also be a side effect of medication or smoking. 

While most causes of a persistent cough are mild and easily treatable, a lingering cough could be a symptom of a more serious health condition. Uncommon but serious conditions that may cause a chronic cough include cancer, lung disease, fungal infections, or heart failure. 

A persistent cough is annoying and can disrupt your quality of life. Getting prompt and effective treatment will help you feel—and sleep—better.