What Causes Cough?

Coughing occurs when the nerve endings in your airways become irritated. Certain irritants and allergens, medical conditions, and medicines can irritate these nerve endings.

Irritants and Allergens

An irritant is something you're sensitive to. For example, smoking or inhaling secondhand smoke can irritate your lungs. Smoking also can lead to certain medical conditions that can cause a cough. Other irritants include air pollution, paint fumes, or scented products like perfumes or air fresheners.

An allergen is something you're allergic to, such as dust, animal dander, mold, or pollens from trees, grasses, and flowers.

Coughing helps clear your airways of irritants and allergens. This helps prevent infection.

Medical Conditions

A number of medical conditions can cause acute, subacute, and chronic cough.

A common cold or other upper respiratory infection most often causes an acute cough. Examples of other upper respiratory infections include the flu, pneumonia, and whooping cough. An acute cough lasts less than 3 weeks.

A lingering cough that remains after a cold or other respiratory infection is gone is often called a subacute cough. A subacute cough lasts 3 to 8 weeks.

Postnasal drip, asthma, and gastroesophageal reflux disease (GERD) most often cause chronic cough. Chronic cough lasts more than 8 weeks.

Postnasal drip is mucus (a slimy substance) that runs down your throat from the back of your nose. This mucus inflames and irritates the throat. A sinus infection, cold, or ongoing contact with irritants and allergens can cause postnasal drip.

Asthma is a long-term lung disease that inflames and narrows the airways. GERD is a condition in which acid from your stomach backs up into your throat.

Other causes of chronic cough include:

• Respiratory infections. A cough from an upper respiratory infection can develop into a chronic cough.
• Chronic bronchitis. This condition occurs when the lining of your airways is constantly irritated and inflamed. Smoking is the main cause of chronic bronchitis.
• Bronchiectasis (brong-ke-EK-ta-sis). This is a condition in which your airways become damaged and can no longer properly move air in and out. The condition usually is due to an infection or other condition that injures the walls of the airways. 
• Lung cancer. In rare cases, a chronic cough is due to lung cancer. Most people who develop lung cancer smoke or used to smoke.
• Heart failure. Heart failure is a condition in which the heart can't pump blood the way it should. Fluid can build up in the body and lead to a number of symptoms. If fluid builds up in the lungs, it can cause a chronic cough.

Medicines

Certain medicines can cause a chronic cough. Examples of these medicines are ACE inhibitors and beta blockers. ACE inhibitors are used to treat high blood pressure (HBP). Beta blockers are used to treat HBP, migraine, and glaucoma.