Updated 23 October 2017

7 myths about cough

A cough is one of the most common reasons people go to the doctor. Although much is known about coughing, there are many half-baked ideas about this common ailment.

A cough is the rapid expulsion of air from the lungs to clear the throat airways of mucus, foreign particles, fluids, microbes and various irritants.

People tend to get worried if a cough lasts more than a week to ten days, but a 2013 review found that the average cough actually lasts around 18 days. After more than eight weeks a cough can be regarded as chronic and it is advisable to seek medical advice. 

Here are seven misconceptions about this common respiratory reflex:

1. All coughs are caused by infections

The occasional cough to clear one’s throat doesn’t indicate a health problem or condition. Frequent bouts of coughing, however, is a sign that there is something more serious irritating the throat. This may or may not be caused by infection.

Infectious causes of cough include the common cold, flu, laryngitis, sinus infections, bronchitis, pneumonia and whooping cough.

Non-infectious causes of cough include post-nasal drip, emphysema, asthma, GERD (gastroesophageal reflux disease) and allergies.

2. Antibiotics will cure a cough

Antibiotics kill bacteria, but do not have any effect on viruses. A cough is most commonly caused by a cold or flu, which are both viral infections, so the answer in most cases is no. Pneumonia may however be caused by bacteria, in which case antibiotics will be effective.

A good reason to avoid using antibiotics for colds and flu is the emergence of "superbugs" that are resistant to antibiotics. In South Africa antibiotic resistance is being driven by the incorrect use of antibiotics by people suffering from a cold.

3. Hot soup can cure a cough

People suffering from colds or flu tend to produce excess mucus (wet cough), which can get into the lungs and result in coughing. Warm liquids like soups are soothing to the throat and decrease irritation and may therefore ease coughing, but cannot cure the respiratory tract infection that – in most cases – caused the cough.

4. All coughs are contagious

A cough may or may not be contagious. A cough that is caused by a viral or bacterial infection will tend to be contagious, whereas coughs that are the result of allergies, asthma or airway irritation are in most cases not contagious at all.

Coughing fit

5. Cough syrups are an effective remedy

Commercial cough syrups typically include cough suppressants like dextromethorphan, which block your cough reflex, and expectorants like guaifenesin, which are supposed to loosen up mucus in the airways. However, studies have found no good evidence that cough meds are any better than a placebo. 

6, There are lots of different types of cough

The truth is that there are in fact only two types of cough, wet (productive) and dry (non-productive).

A dry cough will tickle your throat and is mostly caused by viral infections, smoke, dust or inflammation. A wet or "slimy" cough is caused by phlegm or mucus in the lungs.

7. Vaccination will prevent a cough

CDC cautions that pertussis (whooping cough) vaccines are effective, but not perfect. They typically offer good levels of protection within the first two years of getting vaccinated, but protection decreases over time.

The annual flu vaccine is the best way to avoid the seasonal flu, which will most likely involve coughing. Trivalent (three-component) and quadrivalent (four-component) flu vaccines are available, which means that your flu shot will offer protection against three or four of the most common flu strains. There are however many other flu strains around against which you will not be protected.  

Vaccination will have no effect on non-infectious causes of cough (e.g. post-nasal drip, emphysema, asthma, GERD, allergies).

Read more:

The mechanism of cough

Chronic cough

Treating a cough


Ask the Expert

Cough Expert

Professor Keertan Dheda has received several prestigious awards including the 2014 Oppenheimer Award, and has published over 160 peer-reviewed papers and holds 3 patents related to new TB diagnostic or infection control technologies. He serves on the editorial board of the journals PLoS One, the International Journal of Tuberculosis and Lung Disease, American Journal of Respiratory and Critical Medicine, Lancet Respiratory Diseases and Nature Scientific Reports, amongst others. Read his full biography at the University of Cape Town Lung Institute.

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