What Is Bronchitis?

What Is Bronchitis?

Outline of respiratory system showing the lungs and airways

Bronchitis occurs when the bronchial tubes (airways in the lungs) are irritated by a virus, bacteria, or allergen. This causes a cough that produces yellow or greenish mucus. The cough can be acute (short-term) or chronic (long-lasting or recurring). Smoking or exposure to secondhand smoke is the most common cause of chronic bronchitis.

Inside Healthy Lungs

Air travels in and out of the lungs through the airways. The linings of these airways produce mucus. This mucus traps particles that enter the lungs. Tiny structures called cilia then sweep the particles out of the airways.

Illustration of a healthy airway. It is open with air moving in and out easily

Healthy Airway: Airways are normally open. Air moves in and out easily.

Illustration of healthy cilia and mucus lining the airways

Healthy Cilia: Tiny, hairlike cilia sweep mucus and particles up and out of the airways.

A Nasty Cough

Bronchitis often occurs when a cold or flu virus infects the airways. Once infected, airways become inflamed (red and swollen). Excess mucus forms, triggering a deep “hacking” cough. A second infection, this time due to bacteria, may then occur. Airways irritated by allergens or smoke are more prone to infection.

Illustration of an inflamed airway showing excess mucus that narrows the airway

Inflamed Airway: Inflammation and excess mucus narrow the airway, causing shortness of breath.

Illustration of impaired cilia.

Impaired Cilia: Excess mucus impairs cilia, causing congestion and wheezing. Smoking can paralyze cilia, worsening the problem.

Making a Diagnosis

A physical exam, medical history, and certain tests help your healthcare provider learn what may be causing the cough. This information is used to plan treatment.

Health History

Your healthcare provider may ask about:

  • How long the cough has lasted, and how long it’s been producing mucus.

  • Other symptoms, such as a runny nose, sore throat, or fever.

  • Medications you’ve used to treat symptoms.

  • Whether the problem has occurred before, when, and how often.

  • Smoking or exposure to secondhand smoke.

  • Lung conditions such as asthma or COPD (chronic obstructive pulmonary disease).

  • Factors that increase the risk of complications, such as age and certain health problems.

The Exam

During the exam, your health care provider listens to the chest for signs of congestion. He or she may also check the ears, nose, and throat.

Possible Tests

  • A sputum test for bacteria. This requires a sample of mucus from the lungs.

  • A nasal or throat swab for bacterial infection.

  • A chest X-ray if your health care provider suspects pneumonia.

  • Tests to check for an underlying condition, such as allergies, asthma, or COPD. You may be referred to a specialist for further lung function testing.

Treating a Cough

The main treatment for bronchitis is easing symptoms. Avoiding smoke, allergens, and other things that trigger coughing can often help. If the infection is bacterial, antibiotics may be used. During the illness, limit activity and get plenty of sleep. To ease symptoms:

  • Don’t smoke, and avoid secondhand smoke.

  • Use a humidifier, or breathe in steam from a hot shower. This may help loosen mucus.

  • Drink fluids. They can soothe the throat and may help thin mucus.

  • Sit up or lie with your head and shoulders propped on pillows to relieve congestion.

  • Ask your health care provider whether to use cough medicine, pain and fever medication, or a decongestant.

If Antibiotics Are Prescribed

Is the problem a bacterial infection? If so, antibiotics may kill the bacteria, speed healing ,and prevent further complications. But most cases of bronchitis are caused by cold or flu viruses. Antibiotics don’t treat viral illness. Taking antibiotics when they are not needed increases your risk of getting an infection later that is antibiotic-resistant.  Your health care provider will prescribe antibiotics if he or she thinks they are likely to help. If they are prescribed:

  • Take the medication until it is used up, even if symptoms have improved. If you don’t, the bronchitis may come back.

  • Take them as directed. For instance, some medications should be taken with food.

  • Ask your health care provider or pharmacist what side effects are common, and what to do about them.


A follow-up exam is advised in 2–3 weeks. By this time, symptoms should have improved. An infection that lasts longer may signal a more serious problem.

To Prevent Future Infections

  • Avoid tobacco smoke. If you smoke, quit. Stay away from smoky places. Ask friends and family not to smoke around you, or in your home or car.

  • Make sure that any allergies are identified and  treated.

  • Ask your health care provider about getting a yearly flu shot.

  • Wash hands often. This helps reduce the chance of picking up viruses that cause colds and flu.

Call Your Health Care Provider If:

  • Symptoms worsen, or new symptoms develop.

  • Breathing problems worsen or  become severe.

  • A skin rash, hives, or wheezing develops. Any of these could signal an allergic reaction to antibiotics.

  • Symptoms don’t improve within a week, or within 3 days of taking antibiotics.