A cough is your body's way of responding to irritants in your throat and airways. An irritant stimulates nerves there to send a cough impulse to your brain. The brain signals the muscles of your abdomen and chest wall to give a strong push of air to your lungs to try to expel the irritant.

An occasional cough is normal and healthy. A cough that persists for several weeks or one that brings up discolored or bloody mucus may indicate an underlying condition that requires medical attention. A cough rarely requires emergency care.

A coughing attack can be very forceful — the velocity of air from a vigorous cough through the nearly closed vocal cords can approach 500 miles per hour. Prolonged, vigorous coughing is exhausting and can cause sleeplessness, headaches, urinary incontinence, and even broken ribs.

CAUSES:

An occasional cough is normal. But a cough that persists may signal an underlying problem. A cough is considered "acute" if it lasts less than three weeks; it's "chronic" if it lasts longer than eight weeks (four weeks in children).

Some causes of coughs include:

Common causes — acute

• Common cold
• Influenza (flu)
• Inhaling an irritant
• Pneumonia
• Whooping cough

Common causes — chronic

• Allergies
• Asthma (most common in children)
• Bronchitis
• GERD
• Postnasal drip

Others

• Acute sinusitis
• Bronchiectasis
• Bronchiolitis (especially in young children)
• Choking: First aid (especially in children)
• Chronic sinusitis
• COPD
• Croup (especially in young children)
• Cystic fibrosis
• Emphysema
• Hay fever
• Heart failure (congestive)   
• Laryngitis
• Lung cancer
• Medications called angiotensin-converting enzyme (ACE) inhibitors
• Neuromuscular diseases such as parkinsonism, which weaken the coordination of upper airway and swallowing muscles
• Respiratory syncytial virus (RSV) (especially in young children)
• Tuberculosis

WHEN TO SEE A DOCTOR:

Call your doctor if your cough doesn't go away after several weeks or if you or your child is:

• Coughing up thick, greenish-yellow phlegm
• Wheezing
• Experiencing a fever more than 100 F (38 C)
• Experiencing shortness of breath

Seek emergency care
Seek emergency care if you or your child is:

• Choking
• Having difficulty breathing or swallowing
• Coughing up bloody or pink-tinged phlegm

Self-care measures
To ease your cough, try these tips:

• Suck cough drops or hard candies. They may ease a dry cough and soothe an irritated throat. Don't give them to a child under age 3, however, because they can cause choking.
• Moisturize the air. Use a vaporizer or take a hot, steamy shower.
• Drink fluids. Liquid helps thin the mucus in your throat. Warm liquids, such as broth, tea or lemon juice and honey in warm water, can soothe your throat.

Reference: MayoClinic. http://www.mayoclinic.com/health/cough/MY00108