We cough for many reasons: something “goes down the wrong pipe,” resulting in a brief hacking fest. Our winter throat tickles may signal an imminent cold or flu. We experience that nagging cough that takes weeks to fade after illness. But what about that cough that lingers so long that weeks fade into months?

Coughing is a vital mechanism in the body’s defense against disease. When we cough, we help the body expel mucus, microbes and foreign particles from the respiratory tract, protecting the lungs from infection and inflammation. Chronic, or long-term, cough can be caused by a number of things, from sinus problems to inhaling foreign objects into the lungs (usually seen in children), but the following are 8 common causes of chronic cough:

1.    Asthma or Allergies

For some people, inhaling pollen, dust, pet dander and other airborne particles can trigger a reaction called allergic rhinitis, which can lead to chronic coughing while in the presence of such irritants (like pets) or during certain times of year. Allergic rhinitis coughing usually accompanies other symptoms, like stuffy nose and sneezing. If you suspect that you’re suffering from allergies, you can keep track of what brings on coughing attacks. If your coughing intensifies during spring or when you spend time gardening, or if your cough eases up after leaving your mother’s house and her new kitten, you probably have allergies. If you’re having a hard time pinpointing your allergy, your doctor can run a series of tests to pinpoint the allergen.

Asthma, a chronic lung disease in which the lungs' airways are prone to swelling, causes coughing, typically along with chest tightness, wheezing and shortness of breath. Asthmatics usually have allergy triggers, along with negative responses to exercise, colds, cigarette smoke and airborne irritants.

2.    Chronic Obstructive Pulmonary Disease (COPD)

COPD, a lung condition that includes chronic bronchitis and emphysema, is a common cause of chronic cough. COPD develops when the airways and air sacs in the lungs become inflamed or damage, commonly a result of smoking. The lungs of COPD patients produce excess mucus, which the body tries to expel by coughing. If you suspect that you have COPD, especially if you are a smoker, your doctor may conduct tests to confirm a diagnosis, including spirometry, when a patient is asked to inhale as deeply as possible and then exhale into a tube.