Have you ever wondered, why when we sneezed or coughed, the colour of our mucus is either white or green? Perhaps sometimes, brown or red? Is it a bad thing? If it is a bad thing, how bad can it be?

This article will explain to you about mucus, and why they have variety of colours.

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Mucus is a slippery and stringy fluid substance produced by many lining tissues in the body. It is in your mouth, nose, and sinuses.

Our body produces a lot of mucus, about 1 to 1.5 liters per day. We tend to not notice mucus at all unless it’s production is increased or the quality of mucus has changed, as may happen with different illnesses and conditions. Much of it, is swallowed and we don’t even notice it. But when you are not feeling well, your mucus becomes a lot more noticeable.

Mucus is essential for body function and acts as a protective and moisturizing layer to keep critical organs from drying out.

It acts as a trap for irritants like dust, smoke, or bacteria as it contains antibodies and bacteria-killing enzymes to help fight off infections.

Now, we already know what is mucus and it’s function in our body.

Let’s talk about it’s colours.

Normally, the colour of your mucus should be watery and crystal clear. Changes in the colour of mucus indicates clues to your health.

Other colours it can turn into are:


The stuff in your nose may get thicker and look white. Usually, like common cold or flu. It may contain viruses.

Green or yellow:

This shade is usually a sign that you have a bacterial infection and your cold or flu is progressing. The green colour comes from a protein released from your inflammatory cells. It is a toxic substance that kills the germs.

Red or pink:

Having a red or pink colour, does not mean that it is a beautiful mucus. You may notice blood-tinged mucus if you are sick and coughing a lot. This may come from broken blood vessels in your nose or throat. In some cases, it can also be a sign of cancer. Your doctor can do tests to find out the cause.

Brown or black:

It is common in heavy smokers or people who are around smoke or coal and dust at their job. This type of mucus also shows up in people with chronic lung diseases. The colour comes from a mix of blood and inflammation in the lungs. So, please do not smoke!

White, green, or yellow mucus can clear up on its own, but if you also have sore throat, fever, or chills, let your doctor know. They should also know if your mucus turns to any other shade or is very stringy.

20th July 2019.


Muhammad Aiman Hakim bin Ariffin

Fourth Year Medical Student,

Publication and Information Bureau 2019/2020.

  1. Syahindah binti Kamaruddin
  2. Muhammad Afif Sidqy bin Abdul Rahim





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