A dry cough lasting more than 3 weeks is usually a lingering post-viral cough, postnasal drip, acid reflux, or mild asthma, all common and treatable. Less often, it comes from a medication, ongoing irritant exposure, or early lung disease. Rarely, in a smoker, it needs imaging to rule out something serious. This guide covers the likely causes, in order, and the signs that mean you should get checked soon.

1. Post-Viral (Post-Infectious) Cough

What it is: A dry cough that lingers for weeks after a cold, flu, or other respiratory infection has otherwise cleared up.

Why it happens: A viral infection can leave the airways inflamed and extra sensitive for weeks, so the cough continues even after you feel better.

Common symptoms: A dry, tickly cough that worsens with talking, cold air, or laughing, without fever or thick mucus.

Risk factors: A recent cold, flu, bronchitis, or COVID-19 infection, and exposure to cold or dry air.

When to seek evaluation: If the cough has not started to ease by 6 to 8 weeks, or if new symptoms appear, it is worth having checked.

2. Postnasal Drip (Upper Airway Cough Syndrome)

What it is: A cough caused by mucus draining from the back of the nose and sinuses down the throat.

Why it happens: Allergies, sinus inflammation, or a cold increase mucus production, and the drip down the throat irritates the airway and triggers a cough, often worse at night.

Common symptoms: A frequent need to clear the throat, a feeling of mucus running down the throat, and a cough that is worse when lying down.

Risk factors: Seasonal or year-round allergies, chronic sinus problems, and a recent upper respiratory infection.

When to seek evaluation: If over-the-counter antihistamines or a saline nasal rinse do not help within a couple of weeks, an evaluation can pin down the underlying cause.

3. GERD (Acid Reflux)

What it is: A cough triggered by stomach acid moving up into the esophagus and, in some cases, reaching the throat or airway.

Why it happens: Acid or tiny droplets of refluxed stomach contents can irritate nerve endings in the throat, setting off a cough reflex, sometimes without noticeable heartburn.

Common symptoms: A dry cough worse at night or after meals, along with a sour taste in the mouth, hoarseness, or a frequent urge to clear the throat.

Risk factors: Obesity, eating late at night, smoking, and a history of heartburn or hiatal hernia.

When to seek evaluation: A cough that fits this pattern and does not improve with dietary changes or an over-the-counter acid reducer should be evaluated.

4. Asthma or Cough-Variant Asthma

What it is: A form of asthma in which cough, rather than wheezing or shortness of breath, is the main symptom.

Why it happens: The airways become inflamed and overly reactive to triggers such as cold air, exercise, allergens, or smoke, causing them to narrow and produce a cough.

Common symptoms: A dry cough in spells, often worse at night, with exercise, or after cold air, dust, or strong smells, sometimes with mild chest tightness.

Risk factors: A personal or family history of asthma, allergies, or eczema.

When to seek evaluation: A cough that fits this pattern deserves lung function testing to confirm the diagnosis and start proper treatment.

5. ACE Inhibitor Medication Side Effect

What it is: A dry, persistent cough that develops as a side effect of ACE inhibitor blood pressure medications (drug names commonly ending in "pril," such as lisinopril).

Why it happens: These medications can raise levels of a substance called bradykinin in the airways, which can trigger chronic coughing in some people.

Common symptoms: A dry, tickly cough with no mucus, sometimes starting soon after beginning the medication, sometimes months later.

Risk factors: Taking an ACE inhibitor; the cough is more common in women and in people of East Asian descent.

When to seek evaluation: Do not stop a prescribed medication on your own. Talk to the prescribing doctor, who can switch you to an alternative if the cough is bothersome.

6. Environmental Irritants and Allergies

What it is: A cough caused by ongoing exposure to airborne irritants or allergens rather than an infection.

Why it happens: Smoke, dust, fumes, pet dander, mold, or pollen can irritate the airways, and repeated exposure keeps a cough going for weeks.

Common symptoms: A dry cough that flares in certain places or seasons, often with sneezing, itchy eyes, or a runny nose.

Risk factors: Smoking or secondhand smoke exposure, a home or job with poor air quality, and known allergies.

When to seek evaluation: If avoiding the suspected trigger does not improve the cough within a couple of weeks, further evaluation is a good idea.

7. Chronic Bronchitis or Early COPD

What it is: A long-term inflammation of the airways most often linked to smoking.

Why it happens: Years of exposure to cigarette smoke or other irritants damages the airway lining, causing chronic inflammation and difficulty clearing mucus normally.

Common symptoms: A cough, sometimes dry and sometimes producing mucus, that lasts for weeks and keeps recurring, along with shortness of breath that gradually worsens.

Risk factors: A current or past history of smoking, long-term exposure to air pollution or workplace dust and fumes, and age over 40.

When to seek evaluation: Anyone with a smoking history and a cough lasting several weeks should have lung function tested, since early diagnosis allows treatment that slows disease progression.

8. Lung Cancer or Other Serious Pulmonary Causes (Rare)

What it is: In a small number of cases, a persistent cough is the first sign of a serious lung condition, including lung cancer, tuberculosis, or another structural lung problem.

Why it happens: A tumor, chronic infection, or other growth in the airway can irritate or partially block it, producing a cough that does not respond to usual remedies.

Common symptoms: A cough lasting more than 3 to 8 weeks, especially with blood-tinged sputum, unexplained weight loss, night sweats, or a new hoarse voice.

Risk factors: A current or past smoking history, older age, and exposure to asbestos or other occupational irritants.

When to seek evaluation: A cough past 3 to 8 weeks, particularly in a current or former smoker, should be evaluated with a chest X-ray or other imaging. This does not mean cancer is likely, but it should not be overlooked.

When to Seek Medical Care