Causes and Risk Factors of Cough

Health Conditions Linked to Acute, Sub-Acute, or Chronic Coughs

A cough is simply an abrupt expulsion of air meant to clear an irritant, obstruction, microorganism, or fluid from the airways. A cough can be reflexive (automatic) or induced (something you do intentionally). While a cough is the most common reason people see their primary care doctor, the cause of a cough can vary greatly from the common cold or the flu to allergies, pulmonary disease, or even acid reflux.

Common Causes of Constant Coughing
Verywell / JR Bee

Common Causes

While there will invariably be some overlap in the causes behind acute, sub-acute, and chronic coughs (for example, since chronic illnesses can often have acute flare-ups called exacerbations), how long you've had a cough is often the first clue as to what the underlying cause of it is.

Type Duration of Cough
Acute cough Less than three weeks
Sub-acute cough Three to eight weeks
Chronic cough 

More than eight weeks

Acute Cough

Broadly speaking, an acute cough is either the sign of a rapidly developing infection or an acute exacerbation of a chronic illness.

The most common causes of an acute cough include:

Other clues as to the cause of a cough include the age of the individual, whether the cough is wet or dry, the timing of the cough (day/night), and any accompany symptoms.

Pertussis, for example, tends to affect babies and has a distinctive, dry cough. By contrast, COPD mainly affects adults and has a "chesty" productive cough with plenty of mucus. The presence of fever, chills, and muscle aches can help differentiate infectious causes from non-infectious ones.

These clues can work together to help diagnose the underlying cause of a cough. A detailed medical history (including smoking history, family history, medication use, and previous respiratory infections) is also vital.

Sub-Acute Cough

A sub-acute cough is a "middle-of-the-road" classification that helps separate the causes of an acute cough from those of a chronic cough. Most often, a sub-acute cough is the aftermath of an upper respiratory infection that has simply lingered on.

For a cough lasting between three and eight weeks, the most common causes are:

The diagnosis of a subacute cough is similar to that of an acute cough and includes a physical exam and review of your medical history. If asthma is suspected, bronchoprovocation testing (in which you are exposed to a variety of common asthma triggers) may be ordered.

Post-infectious coughs and mild bacterial sinusitis often resolve on their own without treatment. Absent of severe symptoms, some healthcare providers will prescribe an over-the-counter antihistamine-decongestant combo like Claritin-D for one week, and, if this fails, try a course of oral antibiotics.

Chronic Cough

A chronic cough is one that lasts for more than eight weeks but can sometimes persist for years. Although a chronic cough can be attributed to any number of conditions, the majority of cases are related to a small handful of them.

The seven most common causes of a chronic cause are:

Less common causes of chronic cough include:

  • Sarcoidosis (an inflammatory condition that causes the formation of granular clumps in the lungs and other organs)
  • Tuberculosis (TB)
  • Acute left heart failure
  • Bronchogenic carcinoma (cancer primarily affecting the airways of the lungs)
  • Cancer metastasis (spread of cancer) to the lungs
  • Pharyngeal dysfunction, in which the passage between the mouth and windpipe malfunctions, allowing food and other substances to enter the lungs
  • Psychogenic cough (a habitual cough of psychological origin)

Because the causes of a chronic cough are so diverse, lab testing and imaging studies are usually required. In some cases, the healthcare provider may simply advise you to avoid certain drugs or irritants to see if the cough clears. With ACE inhibitors—drugs most commonly used to control high blood pressure—it can take up to four weeks before a cough fully resolves.

Severe or treatment-resistance cases may need to be referred to a pulmonologist or allergist for further investigation.


Although genetics are usually not considered in the investigation of a cough, there are certain genetic disorders characterized by coughing. These cause neurologic rather than physical defects that lead to pharyngeal dysfunction and dysphagia (difficulty swallowing).

One such condition is known as oculopharyngeal muscular dystrophy (OPMD), which typically manifests with symptoms after age 40. In addition to eye drooping, OPMD can cause weakening of the throat muscles, leading to chronic cough and choking. It is a rare progressive disorder that eventually affects walking and cognitive function.

Autosomal dominant hereditary sensory neuropathy (ADHSN) is another rare inherited disorder characterized by chronic cough and reflux. A hoarse voice, constant throat clearing, and hearing loss (caused by persistent pressure in the external ear canal) are common features. ADHSN is believed linked to a gene mutation at the 3p22-p24 chromosome.

Lifestyle Risk Factors

Any inhaled substance that irritates or obstructs the airways can trigger the cough reflex. Persistent exposure to these substances can lead to a condition known as cough hypersensitivity in which you become abnormally sensitive to inhaled substances. This is related to changes in the brainstem that amplify the nerve signals that induce cough.

While smoking is a common cause—and a lifestyle factor you can readily change⁠—there are other irritants that are just as impactful.

Studies in primates have shown that secondhand smoke increases the excitability of neurons in the brainstem, triggering the cough reflex inappropriately. Ongoing exposure only increases this effect.

There are certain risk factors that can increase your risk of cough hypersensitivity and, with it, the duration or severity of a cough. They include:

  • Smoking (including second-hand smoke)
  • Allergies (especially seasonal allergies)
  • Air pollution
  • Industrial fumes, smoke, dust, and aerosolized chemicals
  • Uncontrolled asthma

Avoidance can go a long way toward reducing the incidence, frequency, and, in some cases, severity of a cough.

A Word From Verywell

Everyone coughs from time to time. Even if you do it frequently, the reason behind it may be something as simple as an irritant in the air or allergies. That said, coughing can be a sign of an acute or chronic issue that may require treatment. When in doubt, seek an evaluation from your healthcare provider.

9 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.
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By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.