Coughing is a protective reflex designed to clear your airways of irritants, mucus, and foreign particles. It happens when sensory receptors lining your throat, windpipe, and lungs detect something that shouldn’t be there and send an urgent signal to your brain to force air out. But when a cough lingers or shows up without an obvious reason, it usually points to one of a handful of common causes.
How the Cough Reflex Works
Your airways are lined with specialized nerve endings that act as sensors. These sensors sit in your throat, windpipe, the branching points of your large airways, and even in less obvious places like your ear canals, diaphragm, and stomach lining. When something irritates them, whether it’s dust, acid, cold air, or excess mucus, they fire a signal through the vagus nerve to a “cough center” in your brainstem.
Your brainstem then coordinates a rapid sequence: you inhale deeply, your vocal cords snap shut, your chest and abdominal muscles contract hard against the closed airway, and then your vocal cords open to release a blast of air at high speed. The whole thing happens in a fraction of a second, and you can’t always stop it, though higher brain centers do give you some voluntary control over the reflex.
There are different types of nerve fibers involved. Some respond quickly to mechanical triggers like particles or pressure changes. Others are slower chemical sensors that react to things like acid, heat, or capsaicin (the compound that makes chili peppers burn). This is why such a wide range of irritants, from a crumb going down the wrong way to stomach acid creeping up your throat, can all trigger the same reflex.
The Most Common Reasons for a Cough
Doctors categorize coughs by how long they last: acute (under 3 weeks), subacute (3 to 8 weeks), or chronic (over 8 weeks). The timeline matters because it points toward different causes.
Short-term coughs are most often caused by upper respiratory infections, the common cold, flu, or COVID. These coughs usually resolve on their own as the infection clears, though some linger into the subacute range as irritated airways take time to calm down.
Chronic coughs that persist beyond 8 weeks tend to fall into three major categories, sometimes overlapping.
Postnasal Drip and Sinus Problems
When your nose and sinuses produce excess mucus, it drains down the back of your throat and physically tickles cough receptors in your larynx and upper airway. But the irritation goes deeper than that. Inflammation in your nasal passages can actually lower the threshold of your entire cough reflex, making your airways hypersensitive to triggers that wouldn’t normally bother you. Studies have shown that stimulating nasal nerves with irritants increased the number of coughs by 60 to 100 percent compared to a control group. So it’s not just the drip itself; your whole cough system gets turned up to a higher sensitivity setting.
Acid Reflux
Stomach acid doesn’t have to reach your throat to make you cough. Reflux can trigger coughing in two ways: acid and digestive enzymes like pepsin can directly irritate the airway if tiny amounts are aspirated, or reflux in the lower esophagus can trigger the vagus nerve and cause a reflex cough even without anything reaching your throat. This is why some people with reflux-related coughs never experience heartburn. The cough is the only symptom.
Asthma (Without Wheezing)
A form called cough-variant asthma presents as a persistent dry cough, often worse at night, with no wheezing, no shortness of breath, and completely normal lung function on standard tests. The airways are hypersensitive and inflamed, but not narrowed enough to cause the classic asthma symptoms. The defining clue is that the cough responds to bronchodilator therapy. Elderly people with asthma are especially likely to present this way, with chronic cough and little or no wheezing.
Why Your Cough Gets Worse at Night
If your cough ramps up the moment you lie down, the reason is often positional. Lying flat lets postnasal drip pool in the back of your throat instead of draining forward. It also allows stomach acid to travel more easily up your esophagus. Both of these directly stimulate cough receptors that were relatively unbothered while you were upright.
Asthma also has a well-documented nocturnal pattern. Airway inflammation and sensitivity naturally fluctuate over a 24-hour cycle, and for many people with asthma, the airways are most reactive during sleep hours. Heart failure can also worsen cough when lying down, as fluid redistributes into the lungs, though this is accompanied by other symptoms like swelling in the legs and shortness of breath with exertion.
Environmental and Workplace Irritants
Your cough may have nothing to do with illness and everything to do with what you’re breathing. Dust, fumes, strong cleaning products, cigarette smoke, and air pollution all activate the same airway nerve fibers that respond to infection or acid. In occupational settings, exposure to substances like silica dust (common in mining, construction, and glass manufacturing), cement dust, and industrial gases can cause chronic cough by repeatedly stimulating the chemical and mechanical sensors in your airways.
If your cough improves on weekends or vacations and returns at work, that pattern is a strong signal that an environmental trigger is responsible.
Medications That Cause Coughing
A class of blood pressure medications called ACE inhibitors causes a persistent dry cough in roughly 2 to 11 percent of people who take them. The mechanism is well understood: these drugs block an enzyme that normally breaks down a compound called bradykinin in your airways. When bradykinin accumulates, it sensitizes the nerve endings in your respiratory tract and triggers the cough reflex. The cough can start within days of beginning the medication or develop months later. It typically resolves within one to four weeks of stopping the drug.
When a Cough Becomes Concerning
Most coughs are annoying but harmless. Certain accompanying symptoms, however, change the picture. Coughing up blood, even a small amount, needs prompt evaluation. The same goes for a cough paired with unexplained weight loss, drenching night sweats, a fever that won’t break, severe shortness of breath, or chest pain. A new cough in a long-term smoker, or a change in the character of an existing smoker’s cough, also warrants attention.
Any cough lasting more than 8 weeks deserves investigation regardless of other symptoms. Chronic cough almost always has an identifiable and treatable cause, but finding it sometimes requires working through the common culprits systematically.
Treating the Cough vs. Treating the Cause
Over-the-counter cough remedies fall into two broad categories: suppressants, which aim to reduce the frequency and intensity of coughing, and expectorants, which thin out mucus so you can clear it more easily. Suppressants make sense when you have a dry, irritating cough that serves no productive purpose. Expectorants are better suited for a wet, mucus-heavy cough where the goal is to get the secretions out, not hold them in.
Neither type fixes the underlying problem. A postnasal drip cough responds to treating the sinus inflammation or allergy driving it. A reflux cough improves with dietary changes, sleeping with your head elevated, and reducing acid production. Cough-variant asthma needs inhaled medications that reduce airway inflammation and reactivity. And a medication-induced cough simply requires switching to a different drug.
The most effective approach to a persistent cough is identifying which of these triggers is responsible. In many cases, more than one factor contributes at the same time, which is why a cough can sometimes resist treatment until all the contributing causes are addressed.