Snot, mucus, nose gravy, phlegm - There are many names for it but we all know about that gross liquid that oozes from your nose and throat whenever we get sick.

It's sticky, gooey, and not particularly nice to be around, but phlegm is an important byproduct whenever your body is fighting against an infection. So let's take a look into what exactly phlegm is, what purpose it serves, and what the colour of your phlegm means.

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So what is phlegm and what purpose does it serve?

Phlegm/mucus/snot comprises of about 95 per cent water, 3 per cent proteins, and 1 per cent salt and other substances, and is a byproduct of inflammation in the sinuses and lungs. While this stuff is pretty unsavoury, it actually assists in fighting infection as it's created by the body to combat illness, ranging from bacterial infections like bronchitis, sinusitis or pneumonia to viral infections.

But it's gross!

Yes it is, but it's normal and just something your body does naturally.

Okay, what about the colour of my phlegm?

There's a misconception that green or yellow phlegm means you definitely have a bacterial infection of some sort and should immediately get on some antibiotics. However, research has shown that this is generally not the case as colourful snot alone isn't enough of a reason to go rushing to the doctor. Having said that, the colour of the phlegm is a pretty good starting indicator of what illness you may have and can help doctors diagnose exactly what's going on.

As for why your phlegm changes colour, this actually comes from white blood cells that fight infection (which results in green or yellow phlegm) or the presence of blood due to inflammation, infection, or side effects of nasal medication (which results in brown phlegm).

Let's take a look at what colours phlegm can be and what it can be an indicator of:

  • White - Allergies, asthma, and viral infections are commonly associated with white or clear phlegm.

  • Green or yellow - This is usually a sign your body is fighting an infection. While the colour is not enough to determine what the infection is, it can be an indicator of a common cold or flu, or infections such as bronchitis, pneumonia, sinusitis, or cystic fibrosis.

  • Red or pink - Blood is usually the cause of any shade of red or pink phlegm and is generally associated with serious illnesses including pneumonia, tuberculosis, congestive heart failure, pulmonary embolism, or lung cancer. See a doctor if you're producing more phlegm than normal, have intense coughing spells, or notice other worrying symptoms such as fatigue or weight loss.

  • Brown - This usually means old blood and is commonly caused by infections such as bacterial pneumonia, bacterial bronchitis, cystic fibrosis, pneumoconiosis, or a lung abscess. See a doctor if you're producing more phlegm than normal, have intense coughing spells, or notice other worrying symptoms such as fatigue or weight loss.

  • Black, charcoal or grey - This is generally associated with people who work in coal mines, factories or those who are heavy smokers. It may also be present after inhaling a high amount of a black substance, such as coal dust. Black/charcoal/grey phlegm may also be caused by illnesses including pneumoconiosis or fungal infection. See a doctor if you're producing more phlegm than normal, have intense coughing spells, or notice other worrying symptoms such as fatigue or weight loss.


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Information sourced from: ABC, The Conversation, HealthLine, and Wexler Medical Centre

Image credit: The Office

All content is created and published for informational purposes only. It is not intended to be a substitute for professional advice. Always seek the guidance of a qualified health professional.

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