Definition

A cough is a forceful release of air from the lungs that can be heard. Coughing is a reflex protects the respiratory system by clearing it of irritants and secretions.

In other words, it helps to keep your throat and airways clear.  Although it can be annoying, coughing helps your body to heal or protect itself. Coughs can be either acute or chronic.
Acute coughs begin suddenly and usually last no more than 2 to 3 weeks. Acute coughs are the kind you most often get with a cold or flu. Chronic coughs last longer than 2 to 3 weeks.

Symptoms

According to Answers.com; “While people can generally cough voluntarily, a cough is usually a reflex triggered when an irritant stimulates a cough receptor found at different points in the respiratory system. These receptors then send a message to the cough center in the brain, which in turn tells the body to cough.

A cough begins with a deep breath in, at which point the opening between the vocal cords at the upper part of the larynx (glottis) shuts, trapping the air in the lungs. As the diaphragm and other muscles involved in breathing press against the lungs, the glottis suddenly opens, producing an explosive outflow of air at speeds greater than 100 mi (160 km) per hour.

In normal situations, most people cough once or twice an hour during the day to clear the airway of irritants. However, when the level of irritants in the air is high or when the respiratory system becomes infected, coughing may become frequent and prolonged.

It may interfere with exercise or sleep, and it may also cause distress if accompanied by dizziness, chest pain, or breathlessness. In the majority cases, frequent coughing lasts one to two weeks and tapers off as the irritant or infection subsides. If a cough lasts more than three weeks it is considered a chronic cough, and physicians will try to determine a cause beyond an acute infection or irritant.

Coughs are generally described as either dry or productive. A dry cough does not bring up a mixture of mucus, irritants, and other substances from the lungs (sputum), while a productive cough does. In the case of a bacterial infection, the sputum brought up in a productive cough may be greenish, gray, or brown. In the case of an allergy or viral infection it may be clear or white. In the most serious conditions, the sputum may contain blood.”

When to see a doctor

Online help from About.com

• Causes of a Chronic Cough
• Sinus Infections Can Cause a Cough
• Cough-Variant Asthma

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