What colour should phlegm be?

What colour should phlegm be?

Effective in preventing germs and bacteria from entering the body, phlegm is a form of mucus that is produced in the lungs and respiratory tract. You may experience it in the back of your throat, potentially leaving you feeling blocked up and congested. But without phlegm, your body wouldn’t have as much protection against bacteria and materials that could cause a serious infection[1].

Phlegm often appears as a clear, thin substance. However, it’s also been known to be an array of different colours and textures. If you’ve found your phlegm to be a peculiar colour and want advice on what it could mean, our guide explains the reasoning behind the different colours phlegm can appear in.

What does the colour of phlegm mean?

If you begin to produce phlegm as the side effect of illness such as a cough, cold, sore throat or an allergic reaction, you may be wondering if its colour is an indication of anything. Phlegm is often produced by the body as a way of combating an issue in the body such as an unwanted irritant, bacteria or virus being present in the body. For example, it could be caused by a number of conditions including asthma, bronchitis, cystic fibrosis, hay fever, lung disease, pneumonia, sinusitis or a respiratory or viral infection[1].

As phlegm could appear as a symptom of a number of different conditions, it can be difficult to know exactly what the cause could be. However, you may be able to use the colour of the phlegm as a way of determining the cause. Below, we look at common colours of phlegm and explain what they could be a sign of.

What does green phlegm mean?

Phlegm turns green when the immune system begins to fight infection in the body. Green phlegm is often the sign of a viral infection, but rarely anything serious that could require antibiotics[2].

In some cases, a healthcare professional may even advise against the use of antibiotics for someone that is producing green phlegm as it may lead to the bacteria building a resistance. However, if the person producing green phlegm also experiences chest pain, difficulty breathing or finds blood in their phlegm, they should seek immediate medical attention.

What does yellow phlegm mean?

Similar to green phlegm, yellow phlegm is also likely to be an indication of the body fighting infection[3]. When the body fights a viral infection, phlegm changes from being transparent to yellow. But if you haven’t noticed the change in colour or simply don’t find an effective solution, the phlegm will thicken and turn green.

Due to this, it’s important that you seek medical attention if you begin to produce green phlegm as it could be a sign that you’ve had a viral infection for some time.

What does brown phlegm mean?

For anyone that begins to produce brown phlegm, it can be concerning as it’s distinctly different in appearance from how phlegm traditionally looks. In many circumstances, brown phlegm is actually blood that has been left in the body for a long period of time and turned darker. Likewise, if phlegm appears to be pink, it could also be caused by internal bleeding. However, if it’s pink, it’s more likely to be fresh.

If you produce pink, red or brown phlegm, it could be a sign of bleeding within the body caused by conditions such as bronchitis, cystic fibrosis, pneumonia or a lung abscess. Whatever the cause, it would be advisable to seek medical attention as soon as you see traces of blood in your phlegm[3].

What does white phlegm mean?

When a nasal cavity is fully or partially blocked, the nose becomes swollen, slowing phlegm from passing through. At this point, the originally clear phlegm becomes thick and cloudy – sometimes even white. As such, white phlegm is common for anyone that is suffering from a cold or the flu[3].

What colour is healthy phlegm?

 As indicated above, phlegm can appear in a variety of colours, but how exactly should it look?

Without any existing problems, healthy phlegm should appear as a thin, clear fluid. You may even experience clear phlegm in your throat as a sign that your body is healthy, with it being present to help keep your respiratory system lubricated. The amount of phlegm then may increase and the visual appearance may change due to an issue with congestion or sinuses, a blockage, a medical condition or an allergic reaction[3].


[1] https://www.nhs.uk/conditions/catarrh/

[2] https://www.gov.uk/government/news/green-phlegm-and-snot-not-always-a-sign-of-an-infection-needing-antibiotics

[3] https://wexnermedical.osu.edu/blog/what-does-the-color-of-your-phlegm-mean