A cough lasting longer than eight weeks in adults (or four weeks in children) is classified as chronic, and it almost always has an identifiable cause. The three most common culprits are sinus drainage irritating the throat, a form of asthma that produces only a cough, and acid reflux from the stomach. But several other conditions and even certain medications can keep a cough going for months.
Sinus Drainage and Upper Airway Irritation
The single most common cause of chronic cough is mucus draining from the nose or sinuses into the back of the throat. You might hear this called post-nasal drip, though doctors now prefer the term upper airway cough syndrome because the cough isn’t always caused by the drip itself. In many cases, the real problem is inflammation directly irritating cough receptors in the upper airway, not just mucus trickling downward.
Allergies, sinus infections, and chronic rhinitis all feed this cycle. You may notice throat clearing, a sensation of something stuck in the back of your throat, or a cough that worsens at night when you lie down. Antihistamines, nasal corticosteroid sprays, and decongestants are the standard first-line treatments, and they often resolve the cough within a few weeks.
Cough-Variant Asthma
Most people picture asthma as wheezing and shortness of breath, but there’s a form where coughing is the only symptom. Cough-variant asthma produces a persistent, usually dry cough that comes in episodes lasting hours or even days. Cold air, weather changes, and exercise are the most common triggers.
Because there’s no wheezing or chest tightness, this type of asthma often goes undiagnosed for months. A breathing test called spirometry, sometimes combined with a challenge test that measures how your airways react to a mild irritant, can confirm it. The treatment is the same as for typical asthma: inhaled corticosteroids and bronchodilators that reduce inflammation and open the airways. About 40% of people with cough-variant asthma eventually develop additional asthma symptoms like wheezing or breathlessness.
Acid Reflux (GERD)
Stomach acid doesn’t have to reach your throat to make you cough. Reflux into the lower esophagus alone can trigger a nerve reflex between the esophagus and the airways that stimulates coughing. This is why many people with reflux-related cough never experience classic heartburn and don’t realize acid is the problem.
When acid does travel high enough to reach the voice box, it can cause what’s known as reflux laryngitis, with redness and swelling around the vocal cords. Making things worse, the physical act of coughing increases pressure in the abdomen and can push more acid upward, creating a self-perpetuating cycle where coughing causes more reflux and reflux causes more coughing. Treatment typically starts with lifestyle changes (elevating the head of the bed, avoiding meals close to bedtime) and, if needed, acid-blocking medications.
Chronic Bronchitis
Chronic bronchitis is defined by a productive cough, one that brings up mucus, lasting at least three months over the course of two consecutive years. It falls under the umbrella of chronic obstructive pulmonary disease (COPD) and is most closely associated with smoking, though long-term exposure to air pollution, dust, or chemical fumes can also cause it. The airways become permanently inflamed and produce excess mucus, and the cough persists because the underlying damage doesn’t fully heal.
ACE Inhibitor Medications
If you take a blood pressure medication in the ACE inhibitor class (names typically ending in “-pril”), it could be the reason for your cough. Clinical data shows that roughly 11% of patients taking these drugs develop a persistent dry cough, a rate far higher than what’s listed on many prescription labels. The cough can start weeks or even months after beginning the medication, which makes the connection easy to miss. Switching to a different type of blood pressure drug usually resolves it completely, often within one to four weeks.
Eosinophilic Bronchitis
This is a less well-known cause that mimics asthma in some ways but behaves differently. In eosinophilic bronchitis, a specific type of immune cell accumulates in the airways and causes inflammation, producing a chronic cough. Unlike asthma, your breathing tests come back normal and your airways don’t narrow or spasm. It’s diagnosed by examining a sample of mucus from the airways for elevated levels of these immune cells. The condition responds well to inhaled corticosteroids, the same anti-inflammatory inhalers used for asthma.
Cough Hypersensitivity
Some people develop a chronic cough because the nerves controlling the cough reflex become oversensitive. This is sometimes called cough hypersensitivity syndrome. The nerves in the airways and throat overreact to stimuli that wouldn’t normally trigger coughing: temperature changes, talking, laughing, or mild irritants like perfume. The underlying problem is neurological rather than structural. Inflammation or damage to the nerves at both the airway level and in the brain’s cough-processing centers can lower the threshold for triggering a cough, so even harmless stimuli set it off.
This diagnosis is often considered when the usual causes have been ruled out and treated without success. It’s increasingly recognized as a distinct condition rather than just “unexplained cough.”
Other Causes Worth Knowing
While the conditions above account for the vast majority of chronic coughs, several less common causes can be responsible:
- Smoking. Active tobacco use is one of the most straightforward causes. The airways are chronically irritated and produce excess mucus. Quitting is the first step doctors recommend before pursuing other workups.
- Infections. A cough that lingers after a cold, flu, or respiratory infection (sometimes called a post-infectious cough) can persist for weeks as inflamed airways heal. Whooping cough and certain fungal or mycobacterial infections also cause prolonged coughing.
- Lung conditions. Bronchiectasis (permanently widened airways that trap mucus), interstitial lung disease, and in rare cases lung cancer can all present with a chronic cough.
How the Cause Is Identified
Doctors typically work through chronic cough in a logical sequence, starting with the most common causes and moving to less common ones only if initial treatments fail. The first step is usually a chest X-ray to rule out pneumonia, lung masses, or other visible lung problems. A CT scan of the sinuses may follow if sinus disease is suspected.
Spirometry, a simple breathing test that measures how much air you can exhale and how quickly, is used to check for asthma and COPD. If standard spirometry looks normal but asthma is still suspected, a challenge test can reveal airways that narrow in response to mild provocation.
In many cases, diagnosis is made through trial treatment rather than a single definitive test. Your doctor may try an antihistamine and nasal spray first, targeting sinus drainage. If the cough persists, inhaled asthma medications are added. If those don’t help, acid-blocking medications are tried for possible reflux. This stepwise approach works because the three most common causes together explain the majority of chronic coughs, and each responds to targeted treatment within a predictable timeframe. When none of these approaches resolve the cough, testing expands to look for less common causes like eosinophilic bronchitis or structural lung problems.
Warning Signs That Need Prompt Attention
Most chronic coughs turn out to be caused by manageable, non-dangerous conditions. But certain symptoms alongside a chronic cough signal something more serious: coughing up blood, unintentional weight loss, progressive shortness of breath, chest pain, or a new cough in someone with a history of smoking. A cough that changes character suddenly, worsens rapidly, or is accompanied by fevers and night sweats also warrants faster evaluation.