A cough that has lasted eight weeks or longer in an adult (or four weeks in a child) is classified as chronic, and it almost always has an identifiable cause. The four most common reasons are postnasal drip (also called upper airway cough syndrome), asthma, acid reflux, and a type of airway inflammation called eosinophilic bronchitis. In many cases, more than one of these is happening at the same time, which is part of why a chronic cough can be so frustrating to pin down.
Postnasal Drip and Sinus Problems
The single most common cause of a chronic cough is mucus draining from the sinuses or nose down the back of your throat. You may feel a tickle, a need to clear your throat constantly, or a sensation of something stuck. Allergies, ongoing sinus infections, and irritants like dust or dry air all keep this cycle going. The cough is often worse at night or first thing in the morning when mucus has pooled while you were lying down.
Treatment usually starts with a nasal steroid spray or antihistamines. If the cough improves within a few weeks, that confirms the diagnosis. Persistent sinus infections may need a longer course of treatment, but imaging of the sinuses isn’t typically necessary unless your symptoms don’t respond to initial therapy.
Asthma Without the Usual Symptoms
Most people picture wheezing and shortness of breath when they think of asthma. But cough-variant asthma produces a dry cough as its only symptom, with no wheezing, no chest tightness, and no obvious breathing difficulty. This makes it easy to overlook. The cough tends to worsen with exercise, cold air, or allergen exposure, and it can be worse at night.
Diagnosis requires a breathing test called spirometry. If results are normal but asthma is still suspected, a bronchial challenge test can reveal whether your airways are unusually reactive. Your doctor may also try a two-to-four-week trial of inhaled anti-inflammatory medication. If your cough clears up, that’s strong evidence you’re dealing with asthma.
Acid Reflux You Might Not Feel
Gastroesophageal reflux disease (GERD) is a surprisingly common cough trigger, and here’s the catch: you don’t need heartburn to have reflux-related cough. Stomach contents rising into the esophagus can stimulate a nerve reflex that triggers coughing, even if the acid never reaches your throat. Non-acid components like bile and digestive enzymes may also play a role.
What makes reflux-related cough especially tricky is that the relationship goes both directions. Coughing itself can force stomach contents upward, creating a self-perpetuating cycle where reflux causes coughing and coughing causes more reflux. If your cough is worse after meals, when lying down, or when bending over, reflux is worth investigating. Dietary changes, elevating the head of your bed, and acid-reducing medications are the usual first steps.
Medications That Cause a Cough
If you take a blood pressure medication in the ACE inhibitor class (names typically end in “-pril”), it could be the culprit. About 4% of people on these drugs develop a persistent dry cough. It can start within weeks of beginning the medication or appear months to years later, which makes the connection easy to miss. The cough resolves after stopping the drug, though it may take several weeks to fully clear. Your doctor can switch you to a different type of blood pressure medication that doesn’t carry this side effect.
Infections That Linger
A respiratory infection is one of the most common triggers for a cough that just won’t quit. Post-infectious cough can persist for weeks after a cold or flu because the airways remain inflamed and hypersensitive even after the infection itself is gone.
Whooping cough (pertussis) deserves special attention. In adults, it often starts looking like an ordinary cold. One to two weeks later, it progresses into violent, uncontrollable coughing fits that can last one to six weeks, sometimes up to ten. You may hear a high-pitched “whoop” sound when inhaling after a fit. People who’ve had it consistently describe it as the worst cough of their lives. Pertussis is frequently underdiagnosed in adults because doctors don’t think to test for it, so mention the possibility if your cough fits this pattern.
Environmental and Workplace Irritants
Chronic exposure to vapors, gases, dusts, and fumes at work can cause or worsen a persistent cough. This includes obvious irritants like chemical fumes and less obvious ones like fine dust from construction materials or industrial processes. After the World Trade Center collapse, 10% of people with high exposure to the alkaline dust developed a chronic cough. Marijuana smoke is another underappreciated irritant that clinicians sometimes forget to ask about.
The timing of your cough is a useful clue. If it’s better on weekends or vacations and worse during the workweek, an occupational exposure is likely. Even if the connection seems subtle, mention your work environment to your doctor, because many people don’t think to bring it up and clinicians don’t always ask.
When Your Cough Nerves Become Oversensitive
Sometimes a chronic cough persists even after every common cause has been treated. This may be cough hypersensitivity syndrome, a condition where the nerves that control the cough reflex become permanently dialed up. A viral infection, allergen exposure, or prolonged irritation can change how nerve cells in the airways respond, lowering the threshold for triggering a cough. The result is that things that shouldn’t make you cough, like talking on the phone, laughing, a change in air temperature, perfume, or eating dry, crumbly food, suddenly do.
People with this condition often describe a persistent tickle or irritation in the throat that never fully goes away. The signals traveling from the airway nerves to the brain become amplified, so even mild stimuli produce an exaggerated cough response. This is a real, physiological process, not a habit or a psychological issue. Treatment typically involves speech therapy techniques that help retrain the laryngeal nerves, and in some cases medications that calm nerve sensitivity.
How a Chronic Cough Gets Diagnosed
The workup usually follows a logical sequence. Your doctor will first look for the obvious and easily fixable: Are you on an ACE inhibitor? Do you smoke? Are you exposed to workplace irritants? A chest X-ray is the standard first imaging test, and it’s enough to rule out most infections, inflammatory conditions, and tumors in the lungs.
If the X-ray is normal and there are no red flags, advanced imaging like CT scans or procedures like bronchoscopy usually aren’t needed right away. Instead, your doctor will likely try treating the most probable cause, whether that’s postnasal drip, asthma, or reflux, and see if the cough improves. Spirometry is essential if asthma is suspected. If spirometry is normal but the suspicion remains, a methacholine challenge test can reveal hidden airway reactivity.
Because multiple causes often overlap, treatment sometimes involves addressing two or three conditions simultaneously. It’s not unusual for someone to have both reflux and postnasal drip contributing to the same cough.
Symptoms That Need Prompt Attention
Most chronic coughs turn out to have a manageable cause, but certain symptoms alongside a cough signal something more serious. Coughing up blood, unexplained weight loss, persistent fever, hoarseness, significant shortness of breath, excessive mucus production, or recurrent pneumonia all warrant prompt evaluation. A smoking history of 20 pack-years or more, or being a current smoker over age 45, also raises the stakes. In these situations, your doctor will likely move more quickly to imaging and specialist referral rather than starting with empiric treatment.