A cough is the sudden explosive release of air from the lungs, which clears respiratory passages of obstruction or irritants such as smoke and mucus; it occurs both on reflex and on volition. Air flow may reach high velocity and potentially infectious particles spread a great distance if the mouth is uncovered. Persistent cough points to an underlying medical condition.

 

A cough is a natural reflex that protects the lungs. By clearing the airways, it also helps prevent infection.

 

Prolonged coughing can cause unpleasant side effects, such as chest pain, exhaustion, light-headedness, and loss of bladder control. Coughing can also interfere with sleep, socializing, and work.

 

Causes

Coughing occurs when the nerve endings in the airways (see bronchial tree) become irritated. Certain irritants and allergens, medical conditions, and medicines can irritate these nerve endings.

 

Irritants and allergens

An irritant is something a person is sensitive to. For example, smoking or inhaling secondhand smoke can irritate the 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 a person is allergic to (see allergy), such as dust, animal dander, mold, or pollens from trees, grasses, and flowers.

Coughing helps clear the 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 that runs down the throat from the back of the 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 the stomach backs up into the 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 the airways is constantly irritated and inflamed. Smoking is the main cause of chronic bronchitis.

Bronchiectasis. This is a condition in which the 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.

 

Diagnosis

Your doctor will diagnose the cause of your cough using your medical history, a physical exam, and the results from tests.

 

Medical history

Your doctor will likely ask questions about your cough. He or she may ask how long you've had it, whether you're coughing anything up (such as mucus), and how much you cough.

 

Your doctor also may ask:

 

About your medical history, including whether you have allergies, asthma, or other medical conditions.

Whether you have heartburn or a sour taste in your mouth. These may be signs of gastroesophageal reflux disease (GERD).

Whether you've recently had a cold or the flu.

Whether you smoke or spend time around others who smoke.

Whether you've been around air pollution, a lot of dust, or fumes.

 

Physical exam

To check for signs of problems related to cough, your doctor will use a stethoscope to listen to your lungs. He or she will listen for wheezing (a whistling or squeaky sound when you breathe) or other abnormal sounds.

 

Diagnostic tests

Based on the results of your medical history and physical exam, your doctor may recommend tests. For example, if you have symptoms of GERD, your doctor may recommend a pH probe. This test measures the acid level of the fluid in your throat.

 

Other tests may include:

 

An exam of the mucus from your nose or throat. This test can show whether you have a bacterial infection.

A chest X-ray. A chest X-ray takes a picture of your heart and lungs. This test can help diagnose conditions such as pneumonia and lung cancer.

Lung function tests. These tests measure the size of your lungs, how much air you can breathe in and out, how fast you can breathe air out, and how well your lungs deliver oxygen to your blood. Lung function tests can help diagnose asthma and other conditions.

An X-ray of the sinuses. This test can help diagnose a sinus infection.

 

Treatment

The best way to treat a cough is to treat its cause. However, sometimes the cause is unknown. Other treatments, such as medicines and a vaporizer, can help relieve the cough itself.

 

Treating the cause of a cough

 

Acute and subacute cough

An acute cough lasts less than 3 weeks. 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 usually goes away after the illness that caused it is over.

 

A subacute cough lasts 3 to 8 weeks. This type of cough remains even after a cold or other respiratory infection is over.

 

Studies show that antibiotics and cold medicines can't cure a cold. However, your doctor may prescribe medicines to treat another cause of an acute or subacute cough. For example, antibiotics may be given for pneumonia.

 

Chronic cough

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

 

Postnasal drip is mucus that runs down your throat from the back of your nose. A sinus infection, cold, or ongoing exposure to irritants and allergens can cause postnasal drip.

 

If you have a sinus infection, your doctor may prescribe antibiotics. If allergens or irritants are the cause of postnasal drip, your doctor may advise you to try to avoid them if possible.

 

If you have asthma, try to avoid irritants and allergens that make your asthma worse. Take your asthma medicines as your doctor prescribes.

 

GERD occurs when acid from your stomach backs up into your throat. Your doctor may prescribe a medicine to reduce acid in your stomach. Waiting 3 to 4 hours after a meal before you lie down and sleeping with your head raised may help relieve GERD symptoms.

 

Smoking also can cause a chronic cough. If you smoke, it's important to quit. Talk to your doctor about programs and products that can help you quit smoking. Also, try to avoid secondhand smoke. Many hospitals have programs that help people quit smoking, or hospital staff can refer you to a program.

 

Other causes of chronic cough include respiratory infections, chronic bronchitis, bronchiectasis, lung cancer, and heart failure. Treatments for these causes may involve medicines, procedures, and other therapies. Treatment also may include avoiding irritants and allergens and quitting smoking.

 

If your chronic cough is due to a medicine you're taking, your doctor may prescribe a different medicine.

 

Treating the cough rather than the cause

Coughing is important because it helps clear your airways of irritants, such as smoke and mucus. It also helps prevent infection.

 

Cough medicines usually are used only when the cause of the cough is unknown and the cough causes a lot of discomfort. Medicines can help control a cough and make mucus easier to cough up. Your doctor may recommend medicines such as:

 

Prescription cough suppressants, also called antitussives. These medicines can help relieve a cough. However, they're usually used when nothing else works. No evidence shows that over-the-counter cough suppressants relieve cough.

Expectorants. These medicines may loosen mucus and make it easier to cough up.

Bronchodilators. These medicines relax your airways.

 

Other treatments also may relieve an irritated throat and loosen mucus. Examples include using a cool-mist humidifier or steam vaporizer and drinking enough fluids. Examples of fluids are water, soup, and juice. Ask your doctor how much fluid you need.

 

Cough in children

No evidence shows that cough and cold medicines relieve a cough in children. These medicines can even harm children. Talk to your child's doctor about your child's cough and how to treat it.

 

Living with a cough

If you have a cough, you can take steps to recover from the condition that's causing the cough. There also are ways to relieve your cough. Ongoing care and lifestyle changes can help you.

 

Ongoing care

Follow the treatment plan your doctor gives you for treating the cause of your cough. Take all medicines as your doctor prescribes. If you're using antibiotics, continue to take the medicine until it's all gone. You may start to feel better before you finish the medicine, but you should continue to take it.

 

Ask your doctor about ways to relieve your cough. He or she may recommend cough medicines. However, these medicines usually are used only when the cause of a cough is unknown and the cough is causing a lot of discomfort.

 

A cool-mist humidifier or steam vaporizer may help relieve an irritated throat and loosen mucus. Getting enough fluids (for example, water, soup, or juice) may have the same effect. Ask your doctor about how much fluid you need.

 

Talk to your doctor about when to schedule follow-up care.

 

Lifestyle changes

If you smoke, quit. Talk to your doctor about programs and products that can help you quit smoking.

 

Try to avoid irritants and allergens that make you cough. Examples of irritants include cigarette smoke, air pollution, paint fumes, and scented products like perfumes or air fresheners. Examples of allergens include dust, animal dander, mold, and pollens from trees, grasses, and flowers.

 

Follow a healthy diet and be as physically active as you can. A healthy diet includes a variety of fruits, vegetables, and whole grains. It also includes lean meats, poultry, fish, and fat-free or low-fat milk or milk products. A healthy diet also is low in saturated fat, trans fat, cholesterol, sodium (salt), and added sugar.