Updated 02 June 2015

How do expectorants work to treat a cough?

A wet, chesty cough is very common in children and it's important that they get relief, even if it's only temporary. This is when an expectorant might the the best answer.


Cough medicines work in different ways, depending on the active ingredient. An expectorant is often one of the ingredients and works by loosening and clearing mucus and phlegm from the lungs, bronchi, and trachea. 

Guaifenesin (also known as glyceryl guaiacolate) is a safe and widely used expectorant in many cough medicines. It is a derivative of the guaiac tree, and was used by the Native Americans for centuries to cure respiratory complaints, colds and the flu. The drug in it's current form was approved for use by the Food and Drug Administration in 1952.

Guaifenesin should, however, not be taken for persistent cough such as occurs with smoking, asthma, emphysema or where cough is accompanied by excessive secretions except under the advice and supervision of a doctor.

Cough medication containing Guaifenesin should also not be given to children under 2 years, unless recommended by a doctor.

How does an expectorant work?

It thins the mucus

What generally happens with a respiratory condition is that the airways leading to the lungs get infected and mucus forms, causing blockage in the lung passages and throat. This blockage causes wheezing, coughing and shortness of breath.

An expectorant thins the mucus, breaking up the fluids that cause congestion and by clearing thick mucus from the airway, making it easier for the mucus to be coughed up. 

Read: The mechanism of cough

Direct expectorants

Direct expectorants are also used to dissolve coughs and they work by inhaling steam from hot water to which certain herbs, such as eucalyptus, ginger and chamomile have been added. The herbal vapours can be quite strong, so direct expectorants is not recommended in children younger than 6.

According to Merck Manuals, these also come in aerosol form and are generally reserved for hospital-based treatment of cough. 

Drinking up to 8 glasses of water a day is another way to thin mucus. 

Read: Side effects of cough medicines

Considerations when giving your child an expectorant

It is important to know what your child's symptoms are and what medications are bested suited to treat their cold or cough before giving them any medicine.

Cough and cold medications are no longer approved for children younger than 4 years old, according to the American Food and Drug Administration, so always talk to your health care provider before giving young children cough medicine. 

When giving kids an expectorant, administer it on its own. Cough suppressants and antihistamines are used to dry up coughs, so don't use them along with a mucus-loosening medicine.

Keeping your child hydrated is important, as this will help keep the mucus flowing.

Read: Q & A for children’s cough and cold medicines

Tips on  giving your child an expectorant:

1. Read the directions on the label for the correct dosage. This is usually based on a child’s age or weight.

2. Use a measuring spoon to make sure you are giving the exact dosage shown on the label.

3. Administer the expectorant with food -kids often have sensitive stomachs and could get an upset tummy when taking medicines.

4. Give your child lots of water or juice after taking the expectorant. 

5. Depending on the severity of your child’s cough, administer the expectorant once every 4 hours, making sure not to exceed six doses in a 24-hour period.

Read More:

Identify your child's cough

Ingredients in cough mixtures

A parent's guide to coughs

Image: Father giving his son medicine from Shutterstock


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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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