We’ve all had coughs that just won’t quit, and there may be several reasons for this annoyance. Experts say that chronic coughing is common and can be caused by allergies, infections, smoking or a more serious condition like lung cancer.

According to WebMD, a chronic cough is one that lasts three months. But don’t wait that long to call your doctor. Get a checkup after a few weeks to make sure it’s not serious and call sooner if you experience shortness of breath, fever or are coughing up blood.

Here are common causes:

• Postnasal drip. Postnasal drip is a common cause of a persistent cough. When a virus, allergies, dust, chemicals, or inflammation irritate your nasal membranes, you get runny mucus that drips out of your nose and down your throat, causing a cough that gets worse when you sleep or lie down,

• Asthma. The muscles around your airway tighten, the lining swells, and the cells produce thick mucus when you have asthma. Coughing helps get more air into those restricted airways. Common triggers for asthma cough include infections, weather, allergies, tobacco, smoke, medications and even exercise.

• Infections. Your cough may not disappear even after you have think you have recovered from cold, flu, COVID-19 infection, or pneumonia. It may take longer to run its course. “During that time, the lungs heal, and new cough receptors are made,” explains Dr. Panagis Galiatsatos, a pulmonary and critical care doctor at Johns Hopkins School of Medicine. It’s like building a house. “You have to clear out the old stuff to put new stuff in. That’s what coughs do.”

• GERD. Dr. Ned Snyder, a gastroenterologist at Kelsey-Seybold Clinic in Houston tells Newsmax that GERD (gastroesophageal reflux disease) affects 20% of the population. In GERD, liquid contents in the stomach back up into the esophagus and irritate the lungs. Besides coughing, heartburn and chest pain are typical symptoms of GERD.

• Blood pressure drugs. ACE inhibitors for reducing blood pressure often cause a chronic dry cough, says Dr. David Hill, clinical research director at Waterbury Pulmonary Associates in Waterbury, Conn. “With a slight change in medication, the cough almost always goes away,” he says.

• COVID-19. When the virus makes people sick, it can cause lung inflammation and a dry cough, among other symptoms that can range from mild to life-threatening, says WebMD. “The prolonged cough from COVID-19 is no different than any other virus that affects your lungs,” says Galiatsatos. “The injured parts of your lungs are trying to clear out the infection and heal.”

• Smoking. Smoking damages the lungs as well as other parts of the body so people experience “smoker’s cough,” which happens when chemicals and particles in tobacco smoke irritate the lungs. The body manufactures mucus to try and get rid of them by coughing.

• Chronic obstructive pulmonary disease (COPD) is a group of diseases including emphysema and chronic bronchitis that make it difficult for air to get in and out of our lungs. One of the first signs of COPD may be a cough that won’t go away, according to the American Lung Association. When you have COPD, you have excess mucus and more frequent coughing. Shortness of breath is another symptom. Over time, COPD can become life-threatening.

• Lung cancer. While chronic cough can be a symptom of lung cancer, if you are a nonsmoker, and don’t have a family history of lung cancer, it’s not the likely diagnosis says Hill. Smoking is the leading cause of lung cancer, but many people who have never smoked can get the disease, so it’s important to check it out.