The same viruses that cause colds often cause acute bronchitis. But you can also develop noninfectious bronchitis from exposure to your own or someone else's tobacco smoke and from pollutants such as household cleaners and smog.
Bronchitis may also occur when acids from your stomach consistently back up into your food pipe (esophagus) and a few drops go into your upper airway, a condition known as gastroesophageal reflux disease (GERD). And workers exposed to certain dusts or fumes may develop occupational bronchitis, an acute disease that generally clears up when exposure to the irritant stops.
Sometimes inflammation and thickening of the lining of your bronchial tubes become permanent â€” a condition known as chronic bronchitis. You're generally considered to have chronic bronchitis if you cough most days for at least three months a year in two consecutive years. Often, however, smokers with chronic bronchitis cough almost every day, even if it's just to "clear their throats" in the morning.
Unlike acute bronchitis, chronic bronchitis is an ongoing, serious disease. Smoking is the major cause, but air pollution and dust or toxic gases in the environment or workplace also can contribute to the condition
For either acute bronchitis or chronic bronchitis, signs and symptoms may include:
Production of mucus (sputum), either clear or white or yellowish-gray or green in color
Shortness of breath, made worse by mild exertion
Slight fever and chills
If you have acute bronchitis, you may have a nagging cough that lingers for several weeks after the bronchitis resolves. However, bronchitis symptoms can be deceptive. You don't always produce sputum when you have bronchitis, and children often swallow coughed-up material, so parents may not know there's a secondary infection. You can develop chronic bronchitis without first developing acute bronchitis. And many smokers have to clear their throats every morning when they get up, which, if it continues for more than three months, may be chronic bronchitis.
Symptoms of chronic bronchitis
If you have chronic bronchitis, long-term inflammation leads to scarring of the bronchial tubes, producing excessive mucus. Over time, the lining of the bronchial tubes thickens, and your airways eventually may become scarred. Signs and symptoms of chronic bronchitis may also include:
Cough that's worse in the mornings and in damp weather
Frequent respiratory infections (such as colds or the flu) with a worsening productive cough
If you have chronic bronchitis, you're likely to have periods when your signs and symptoms worsen. At those times, you may have superimposed acute bronchitis, either viral or bacterial, in addition to chronic bronchitis.