Science Focus - the home of BBC Science Focus Magazine
Is swallowing your own phlegm harmful? © Getty Images

Is swallowing your own phlegm harmful?

Subscribe to BBC Science Focus Magazine and get 6 issues for just £9.99

Are you sure you have the guts to find out?

Asked by: Richard Williams, Burntwood

Advertisement

Phlegm is the mucous secretion of the respiratory passages. The cilia cells that line these passages are continually driving the phlegm upward to the throat, where it triggers the swallow reflex so that dust and other foreign bodies can be removed from the lungs.

When you are healthy, your phlegm is thin and clear and despite swallowing about 1.5 litres every day, you hardly notice. If you have a cold or other respiratory infection, or you are a heavy smoker, your phlegm may be thicker and darker coloured. This is caused by trapped particles, bacteria, viruses, white blood cells and antibodies.

As unappetising as this cocktail may sound, there isn't really very much more harm that can come to you from swallowing it. Any pathogens have just come from your lungs where they already had almost direct access to your bloodstream. In your stomach they will be destroyed by powerful acids and enzymes and isolated from your body by the thick mucus layer on the stomach wall.

Read more:

Advertisement

Authors

luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.

Advertisement
Advertisement
Advertisement

Sponsored content