Possible Causes and Evaluation of a Persistent Cough

What could be the reason behind your lingering cough?

In This Article

A persistent cough or a chronic cough is a common symptom with many possible causes. Annoying effects of coughing, such as loss of sleep, sore chest muscles, and leaking urine can affect your quality of life and interfere with your daily activities.

If your cough is lingering, you might also be wondering if it could be something worse than a cold or allergies. What does it mean if you have a cough that just won't go away?

Definition

A persistent cough is defined as a cough that persists for a period of eight weeks or longer. The cough may be dry or productive, in other words, you may or may not cough up mucus (sputum). The cough may also be referred to as "chronic," "lingering," or "nagging."

A subacute cough, in contrast, refers to a cough that lasts three to eight weeks, and an acute cough lasts less than three weeks, such as those that occur with the common cold.

Possible Causes

What's causing my child's cough?
Illustration by Alexandra Gordon, Verywell

There are many possible causes of a persistent cough. For the sake of quick comparison, here's a snapshot of common and relatively rare causes of chronic coughs. You'll see that some of these are more likely to affect kids than adults and vice-versa.

Though the most common causes are not usually serious, it's important to talk about the less common but significant causes as well, especially for those who are over the age of 50. A significant number of people who are diagnosed with lung cancer are first diagnosed—in error—with some of these more common causes.

Most Common Causes in Adults

The quote that "common things are common" is often the first step when you see your doctor for a persistent cough. The four most common causes (in an average person) include the following.

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. All of these are also referred to as "upper airway" causes. With seasonal allergic rhinitis, you may note a pattern to the cough, but year-round causes of allergies may not suggest a pattern.

Asthma

Though people with asthma often have other symptoms, such as wheezing and shortness of breath, in some people with asthma a cough is the only symptom (cough-variant asthma).

Acid Reflux

Gastroesophageal reflux disease (GERD) is the third most common cause of a chronic cough and is often overlooked. For some people, typical symptoms such as heartburn may not be present, and the only symptom may be a chronic cough. A cough due to GERD is usually worse at night after lying down in bed.

Eosinophilic Bronchitis

Even though many people have not heard of eosinophilic bronchitis, it is one of the top four causes of chronic cough in adults. Eosinophilic bronchitis is similar to asthma in some ways based on the type of immune cells present, but these cells are drawn to a different part of the airway.

The diagnosis can be somewhat challenging as lung function tests are usually normal, but the condition usually responds to inhaled steroids.

Most Common Causes in Children

The causes of chronic cough in a very young child is beyond the scope of this article, but the most common causes of 6- to 14-year-old children in a 2017 study were:

  • Asthma (also in the adult list)
  • Protracted bacterial bronchitis
  • Upper airway cough syndrome (with causes similar to those listed for adults above)

Other Common Causes

Still common, but further down the list, are these causes:

  • Smoking: Unfortunately, it is often difficult to distinguish a smoker's cough from a cough due to other conditions such as lung cancer.
  • Infection: A persistent cough may be the lingering cough of whooping cough (pertussis). Children who have been immunized may still get whooping cough and the incidence in adults is increasing. Worldwide, a common symptom of tuberculosis is a chronic cough.
  • Medications: Studies from around the world have reported that people treated with ACE inhibitors develop a chronic cough and discontinue using the medication. Examples include Vasotec (enalapril) and Zestril (lisinopril).
  • Upper airway cough syndrome: A post-infectious cough can sometimes linger for many weeks following an upper respiratory infection.
  • Chronic bronchitis: Chronic bronchitis is a form of chronic obstructive pulmonary disease (COPD) that often occurs in people who smoke but may also be related to environmental exposures and other factors.

Less Common Causes

These causes are seen less often:

  • Lung cancer: For only 2% of people with a persistent cough, lung cancer is the underlying cause. Characteristics of a cough related to lung cancer can be difficult to distinguish from a cough due to other causes. On the other side of the coin, roughly 57% of people with lung cancer have a cough.
  • Other benign and malignant lung tumors: 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 coccidiomycosis, histoplasmosis, and tuberculosis.
  • Sarcoidosis: Sarcoidosis is a poorly understood 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.
  • Heart failure: Fluid build-up in the lungs caused by heart failure can lead to persistent coughing or wheezing. Blood-tinged mucus may be produced.

There are more causes of a persistent cough, but the important point is to note that there are a number of causes and a careful evaluation is needed if your cough is not going away.

When to Worry

Many people worry about a chronic cough being a symptom of lung cancer, and this is for good reason.

Roughly half of people with lung cancer have a persistent cough at the time of diagnosis, and 2% of people who present to their doctor with a chronic cough will have lung cancer.

The time between the onset of symptoms (such as a persistent cough) and a diagnosis of lung cancer can be several months, and we know that lung cancer is most curable in the early stages.

There are some ways in which a lung cancer cough can be different, but the truth is that there is much overlap, and you can't really tell from a cough alone whether someone is likely to have lung cancer.

It's also important to note that a chest X-ray can easily miss lung cancer. A significant number of people who are diagnosed with lung cancer have had a "normal" chest X-ray in the year preceding their diagnosis.

As a final note about lung cancer, keep in mind that non-smokers get lung cancer too—up to 20% of people who die from long cancer have never smoked or used tobacco.

When to See Your Doctor

It is important to make a doctor appointment if you have a cough that persists, even if you believe there is a reason to explain your cough such as continued smoking or allergies. You should call your doctor immediately if you experience chest pain, shortness of breath or lightheadedness, or are coughing up blood.

Questions your doctor may ask 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)?

Diagnosis

Depending on the severity of your cough, your doctor will first want to control your symptoms to make you feel more comfortable. They will then recommend tests to determine the cause.

Your doctor will first take a careful history, asking you about any risk factors for conditions which may cause a cough as well as whether you have recently traveled. Blood tests may be done to look for any evidence of infection.

A chest X-ray is often done first. But it's important to note that a chest X-ray can sometimes miss the causes of a chronic cough.

A computerized tomography (CT) scan can give further information when looking to see if there is any evidence of a tumor or infection. If you have symptoms of sinusitis, a CT scan of your sinuses may be recommended.

Other tests which may be recommended include:

  • Allergy tests
  • Pulmonary function tests to screen for lung conditions such as asthma and emphysema
  • Esophageal pH testing to test for present acid reflux as a possible cause of a persistent cough
  • Bronchoscopy to check for foreign bodies or evaluate your airways for a tumor
  • Laryngoscopy to examine your throat and voice box

Treatment

Treatment will depend on the underlying cause, as well as the degree to which your cough is interfering with your day-to-day activities.

A Word From Verywell

If you have a chronic cough, the importance of getting checked out can't be stressed enough. It can be frustrating, especially if nothing seems to show up on tests, but hang in there. A chronic cough is not normal.

Get a second opinion if you do not feel like you are being heard, or if you are not getting answers. Many of the causes—some of which are difficult to diagnose—of a chronic cough require treatment, and treatment may be more effective if these conditions are found earlier rather than later.

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