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A cough is a sudden, noisy expulsion of air from the lungs.

What is going on in the body?

Coughing is usually a reflex response of the diaphragm and respiratory muscles caused by an irritation in the throat or windpipe. A reflex response means that the body does something automatically, without a person thinking about it.

The cough reflex helps to protect the lungs from bacteria, viruses, dust, and other damaging substances. However, people can cough on purpose if they want or need to. There are many possible causes of a cough, ranging from allergies to lung infections and cancer.

What other signs and symptoms are associated with this symptom?

A cough generally comes to the attention of a healthcare professional only if it persists over several hours or days. In this instance, the professional needs to know:

• if anyone else who has been near the person has been coughing or sick
• if the cough is constant or only occasional
• if the cough is dry or brings up any mucus or phlegm and the color of the phlegm
• when the cough started and how long it has been going on
• whether any blood has been coughed up
• whether the cough seems to recur at a certain time of year, which often happens when a person has seasonal allergies
• whether the individual has a fever, heartburn, runny nose, or weight loss.

What are the causes and risks of the symptom?

There are a number of things that can cause a cough, including the following:

• ACE inhibitors, which are medications that are often used to treat high blood pressure
• allergies
• asthma
• chronic obstructive pulmonary disease, also called COPD, such as emphysema
• congestive heart failure, which can cause fluid buildup in the lungs and make a person cough
• exposure to certain chemicals or gases, such as car exhaust
• a foreign body in the windpipe, which can happen when a small child puts objects in his or her mouth
• gastroesophageal reflux (heartburn)
• lung or throat infections, such as strep throat, acute bronchitis, or pneumonia
• miscellaneous conditions, such as a neurological disorder known as Tourette syndrome
• postnasal drip syndrome, which occurs when mucus from the nose and sinuses drains down the back of the throat
• smoking
• tumors or cancer, including lung cancer

Other causes are also possible. Sometimes no cause can be found for a person's coughing.

What can be done to prevent the symptom?

Preventing a cough depends on what is causing it. Quitting smoking will eventually get rid of a smoker's cough, though at first the person may cough up more phlegm than usual, as his or her airways recover.

Early treatment of gastroesophageal reflux and congestive heart failure can prevent coughing from these conditions or from the medication prescribed for them. Many cases of coughing cannot be predicted or prevented, but they can be treated.

How is the symptom diagnosed?

Sometimes, the reason for the cough is obvious to the healthcare professional from the history and physical exam. In other cases, blood tests or a chest X-ray may be needed, depending on what is suspected. Pulmonary function tests can help to diagnose asthma or emphysema

What are the long-term effects of the symptom?

A cough that is severe can be annoying and prevent sleep and other activities. Most long-term effects are related to the underlying cause. For example, those who have lung cancer as the cause of their cough may die. Those who have acute bronchitis usually get better within a few weeks and have no long-term effects at all.

What are the risks to others?

If the cause of a cough is a bacterial or viral infection, the person can spread these organisms to others.

What are the treatments for the symptom?

The underlying cause of the cough should be treated if possible. Medications such as dextromethorphan or codeine can be used to suppress a cough. Persons with a tumor or cancer may need surgery, radiation therapy, or chemotherapy. Those who have a lung infection may need antibiotics.

Persons with asthma or emphysema may need medications to reduce the inflammation in the lungs and to help open the airways. Individuals taking ACE inhibitors for high blood pressure may need a different type of medication.

What are the side effects of the treatments?

Medications used to treat coughing may cause drowsiness, stomach upset, or allergic reactions. Surgery can be complicated by bleeding, infection, or an allergic reaction to the anesthetic

What happens after treatment for the symptom?

A person with asthma or emphysema may need treatment for life. Persons with infections such as acute bronchitis may need no further treatment or monitoring after they recover.

How is the symptom monitored?

An individual can monitor his or her cough and how it is responding to treatment. Any new or worsening symptoms should be reported to the healthcare professional.