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By Bjarne Lühr Hansen PhD, MD and Philipp Skafte-Holm MD, Mentor Institute

Cough cleans your lungs for slime. Cough medicine is only rarely necessary. Prolonged cough and thick, yellow or green sputum can be signs of more serious illness. If you do not have a fever, you do not have pneumonia. If you have trouble breathing, you must call the doctor immediately.

Cough is a reflex from the lungs. The reflex is triggered, when the lungs are irritated by for example smoke, slime or snot. If you cough, the three questions mentioned below are important:

Do you have a fever?

If you have a fever, the cause of your cough may be inflammation of the airways. The inflammation can be located in the sinuses and the throat (e.g. sinusitis or tonsillitis), in the upper part of the lungs (e.g. bronchitis) or in the bottom part of the lungs (e.g. pneumonia).

If you do not have a fever, you do not need to worry about having pneumonia. This is also true for walking pneumonia.

Is there sputum?

If there is sputum, the cause is most often inflammation of your airways. Sputum that is thick, yellow or green is together with fever sign of bacterial inflammation while thin and clear sputum is sign of viral inflammation. Bacteria require treatment with antibiotics, while viral inflammations pass by themselves. If you do not cough up slime, the cough is called dry cough. Dry cough is frequently seen with asthma.

How long have you been coughing?

A brief cough with no fever (1 to 2 weeks) is often sign of a light common cold. A prolonged cough (more than 2 weeks) can be sign of bronchitis or asthma.

The most common cause of cough is common cold but also bronchitis, pneumonia and asthma can cause cough. More serious lung diseases can also cause cough. Therefore, you should not have a cough for too long without being examined.

Bronchitis is most often caused by virus. The illness starts with uneasiness, headache, a head cold, and irritation of the throat that is followed by cough, hoarseness and light fever. Bronchitis lasts from a few days up to 1 week. It is rarely necessary with penicillin when you have bronchitis.

Common cold is caused by virus. Common cold starts with stuffiness in the nose, snotty nose, loss of sense of smell, possible sneezing and light headache. After a few days, the snot from the nose becomes unclear and cough arrives. Normally, there is no fever. A common cold lasts around 1 week. It does not help to take antibiotics when you have a common cold.

Pneumonia begins as a common cold. Instead of recovering in a few days like with a common cold, you suddenly become pretty ill with chills, fever, chest pains and cough. The chest pains worsen when you take a deep breath. Later, most people have trouble breathing. Persons with other lung diseases (smoker’s lungs, asthma or lung cancer) or with heart diseases (weak heart) have pneumonia particularly easy. Most people who have pneumonia are treated with penicillin or another antibiotic.

Asthma appears by attacks of cough, squeaking breathing and trouble with breathing. The attacks can last from a few hours to several days and are triggered by strain (e.g. running or bicycling), contact with furry animals (e.g. dog or cat), pollen in the air (e.g. birch, mugwort or grass) or by smoke, moisture and house dust. Often, asthma appears late at night or early in the morning. Dry irritated cough, especially during the night, can be a sign of asthma.

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Common cold and bronchitis are highly contagious conditions, since virus is transmitted by cough through the air. Pneumonia is less contagious.

When can I go to work?

When you have neither fever nor trouble breathing.


The cough reflex is a natural defence mechanism against smoke, slime or snot and should not be suppressed. Therefore, cough medicine is rarely necessary. Bacteria demand treatment with penicillin or other antibiotic, while viral inflammations pass by themselves.

What can you do?

Raising the bedhead can help improve breathing and reduce the cough reflex. If you have a fever, you should dress lightly and drink plenty of fluid.

Contact the doctor tomorrow

If you continue to cough after the common cold has passed. If you cough up thick green or yellow slime and you have a fever. If you have a fever and your lungs hurt when you take a deep breath. If you have had the cough for more then 2 weeks.

Contact the doctor immediately

If you have trouble breathing.