Bronchitis is the inflammation of the lining of the airways, or bronchial tubes.  When your airways are inflamed and/or infected, less air is able to flow to and from the lungs and you cough up heavy mucus or phlegm.  There are two types of bronchitis: acute and chronic. A cute bronchitis can accompany a cold and clears up after a week or two.

A person with chronic bronchitis has a mucus-producing cough most days of the month, three months of a year for two years in a row without other underlying disease to explain the cough. After a long period of irritation:

• Excess mucus is produced constantly 
• The lining of the airways becomes thickened 
• An irritating cough develops 
• Air flow may be hampered 
• The lungs become scarred

The airways then make an ideal breeding place for infections.

Chronic bronchitis doesn't strike suddenly.  After a winter cold seems cured, you may continue to cough and produce large amounts of mucus for several weeks.  Since people who get chronic bronchitis are often smokers, the cough is usually dismissed as only "smoker's cough."

As time goes on, colds become more damaging.  Coughing and bringing up phlegm last longer after each cold. Without realizing it, you may begin to take this coughing and mucus production as a matter of course, all year long.  Generally, the cough is worse in the morning and in damp, cold weather.  You may cough up an ounce or more of yellow mucus each day.

In 2009, it was estimated that 9.9 million Americans reported a physician diagnosis of chronic bronchitis.  A person with chronic bronchitis also may develop emphysema.  These two conditions together are commonly referred to as Chronic Obstructive Pulmonary Disease (COPD).

Taken from American Lung Association

People often ignore the signs of chronic bronchitis until it is advanced, because they mistakenly believe that the disease is not life-threatening.  But if you wait to seek treatment, your lungs may already have been seriously injured. This puts you in danger of developing serious respiratory problems or heart failure.  The good news is that chronic bronchitis can be found early and there is much that can be done to treat and help manage the disease.

What Causes Chronic Bronchitis?

Cigarette smoking is by far the most common cause of chronic bronchitis.  The airways of people with chronic bronchitis may also have been irritated initially by bacterial or viral infections.

People exposed to industrial dusts and fumes in the workplace, such as coal miners, grain handlers, and metal molders, are also at high risk of developing this disease.  Air pollution can worsen chronic bronchitis symptoms.

.