Possible Causes and Evaluation of a Persistent Cough

What could be the reason behind your lingering cough?

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. It may be a dry cough or you may cough up mucus (sputum) with a productive cough.

A persistent cough may also be referred to as "chronic," "lingering," or "nagging."

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

Possible Causes

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

There are many possible causes of a persistent cough. Most of the time, treatment can help alleviate the cough so you can sleep better, have more energy, and stop having chest soreness from coughing.

Though the most common causes are not usually serious, sometimes a cough can have a serious cause, such as lung cancer.

Most Common Causes in Adults

The most common causes of a cough are not the same for children and adults, and the evaluation and treatment of a persistent cough will depend on a person's age, other associated symptoms, and past medical history.

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

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 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.

Most Common Causes in Children

The 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

Other Common Causes

Less common, but not rare, causes of a chronic cough include:

Less Common Causes

There are many other less common conditions that can cause a cough. Some of these are 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 percent of people with a persistent cough, lung cancer is the underlying cause. And roughly 57 percent 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 coccidiomycosis, histoplasmosis, and tuberculosis.
  • 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 it can lead to an infection.
  • Heart failure: Fluid build-up in the lungs caused by heart failure can lead to persistent coughing or wheezing with blood-tinged mucus.

Should You Worry?

The causes of a cough are so varied, and they are treated very differently. While there is no need to worry, it is never a good idea to ignore a persistent cough.

There are many different symptoms of lung cancer, and a cough can be one of them.

Roughly half of people with lung cancer have a persistent cough at the time of diagnosis, and 2 percent of people who have a chronic cough find out that they 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.

You can't really tell whether you are likely to have lung cancer based on the characteristics of your cough. A diagnosis of lung cancer relies on biopsy and imaging studies.

It's also important to note that a chest X-ray might not identify lung cancer.

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 Healthcare Provider

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

You should get immediate medical attention if you experience chest pain, shortness of breath or lightheadedness, or are coughing up blood.

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?

Diagnosis

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

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, it is important that you get it checked out. Serious causes, such as cancer, have a better outcome when treatment is started early. Even if your cough is not from a serious cause, you will feel more comfortable—and get better sleep—once it's effectively treated.

Frequently Asked Questions

  • What is a persistent cough?

    A persistent cough is a cough that continues on and off for a period of eight weeks or more. It is sometimes called a chronic, lingering, or nagging cough. A persistent cough can be a wet or dry cough and may initially be triggered by illness, allergy, or asthma. 

  • What causes a persistent cough?

    Postnasal drip is a common cause of a persistent cough. This can be due to allergies, a lingering cold, a sinus infection, or nasal polyps. Asthma—in particular, cough-variant asthma—or acid reflux can also be the reason for a chronic cough. Smoking, ACE inhibitors, and long COVID can also cause a persistent cough as can chronic obstructive pulmonary disease (COPD).

    Less common causes include lung cancer, tumors in or near the lungs, emphysema, bronchiectasis, sarcoidosis, tuberculosis, and heart failure. 

  • What is a long-COVID cough like?

    A COVID cough is typically a dry cough that can linger for weeks or months after having a COVID infection. While the cough is typically dry, some people can experience a wet—or productive—cough.

    If you are experiencing a lingering COVID cough, talk to your doctor. You may need prescription medications to treat the cough.

    Things you can try to help calm a COVID cough include staying hydrated, drinking warm water or tea with honey and lemon, sucking on hard candy or cough lozenges, or taking over-the-counter cough medicine.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Gibson P, Wang G, Mcgarvey L, et al. Treatment of unexplained chronic cough: CHEST guideline and expert panel report. Chest. 2016;149(1):27-44. doi:10.1378/chest.15-1496

  2. Irwin RS, French CL, Chang AB, Altman KW. Classification of cough as a symptom in adults and management algorithms: CHEST guideline and expert panel report. Chest. 2018;153(1):196-209. doi:10.1016/j.chest.2017.10.016

  3. Harvard Health Publishing, Harvard Women's Health Watch. By the way, doctor: what causes acid reflux in the throat?

  4. Brightling CE, Ward R, Woltmann G, Bradding P, Sheller JR, Dworski R, Pavord ID. Induced sputum inflammatory mediator concentrations in eosinophilic bronchitis and asthma. Am J Respir Crit Care Med. 2000 Sep;162(3 Pt 1):878-82. doi:10.1164/ajrccm.162.3.9909064

  5. Michaudet C, Malaty J. Chronic cough: Evaluation and management. Am Fam Physician. 2017;96(9):575-580.

  6. Field SK, Escalante P, Fisher DA, Ireland B, Irwin RS. Cough due to TB and other chronic infections: CHEST guideline and expert panel report. Chest. 2018;153(2):467-497. doi:10.1016/j.chest.2017.11.018

  7. Ng LP, Goh PS. Incidence of discontinuation of angiotensin-converting enzyme inhibitors due to cough, in a primary healthcare centre in Singapore. Singapore Med J. 2014;55(3):146-9. doi:10.11622/smedj.2014034

  8. French CT, Irwin RS. Cough. Am J Respir Crit Care Med. 2016;194(8):P15-P16. doi:10.1164/rccm.1948P15  

  9. Irwin RS, Baumann MH, Bolser DC, Boulet LP, Braman SS, Brightling CE, Brown KK, Canning BJ, Chang AB, Dicpinigaitis PV, Eccles R, Glomb WB, Goldstein LB, Graham LM, Hargreave FE, Kvale PA, Lewis SZ, McCool FD, McCrory DC, Prakash UBS, Pratter MR, Rosen MJ, Schulman E, Shannon JJ, Hammond CS, Tarlo SM. Diagnosis and management of cough executive summary: ACCP evidence-based clinical practice guidelines. Chest. 2006 Jan;129(1 Suppl):1S-23S. doi:10.1378/chest.129.1_suppl.1S

  10. American Heart Association. Warning signs of heart failure.

  11. Gildea TR, Dacosta byfield S, Hogarth DK, Wilson DS, Quinn CC. A retrospective analysis of delays in the diagnosis of lung cancer and associated costs. Clinicoecon Outcomes Res. 2017;9:261-269. doi:10.2147/CEOR.S132259

  12. Del ciello A, Franchi P, Contegiacomo A, Cicchetti G, Bonomo L, Larici AR. Missed lung cancer: when, where, and why? Diagn Interv Radiol. 2017;23(2):118-126. doi:10.5152/dir.2016.16187

  13. American Cancer Society. Lung cancer risks for non-smokers.

  14. Turner RD, Bothamley GH. Chronic cough and a normal chest X-ray - a simple systematic approach to exclude common causes before referral to secondary care: a retrospective cohort study. NPJ Prim Care Respir Med. 2016;26:15081. doi:10.1038/npjpcrm.2015.81

Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."