What does the colour of your phlegm mean? From a cold to pneumonia and even lung cancer we break down how the hue of your mucus reflects your health

As the icy weather approaches, many start coughing and spluttering while they battle winter colds and flu.

Although for most coughing up mucus is part of the cold season, coloured phlegm can be a sign of something more sinister.

From green and yellow to red and even black, off-hue mucus can signal everything from pneumonia, TB and, in severe cases, lung cancer.

Phlegm is a type of mucus produced in the chest, which we make every day to clear irritations from our throats and keep our airways moist.

However, it is not until most become unwell that they even notice they are coughing it up.

Although the green-yellowy tinge of phlegm during colds usually clears up within a few weeks, it can be a sign of something more serious if accompanied by chest pain or shortness of breath. 

Green or yellow

Green-yellow stained phlegm is usually a sign your body is fighting an infection, such as a cold.

This mucus, also known as sputum, usually starts off as yellow and gradually turns green.

However, more serious infections such as bronchitis and sinusitis can also create phlegm of a similar hue.

Lung diseases like chronic obstructive pulmonary disease, which cause difficulty breathing, may also be to blame.

'If you have COPD then there is a good chance it means you have a bacterial infections because people with COPD are much more likely to have bacteria living on their lungs, and that may mean you need antibiotics,' GP Dr Sarah Jarvis told The Sun.

Pneumonia and cystic fibrosis sufferers also often produce mucus that ranges from yellow and green to brown and red.

Brown

Brown phlegm that appears 'rusty' is often a sign of old blood in the mucus.

This can occur after producing sputum that was red or pink.

As well as being a sign of bacterial pneumonia, brown phlegm can also be due to chronic bronchitis, which often affects smokers, and cystic fibrosis.

Inhaling dangerous substances, like asbestos, can also cause incurable lung disease that leads to brown phlegm.

In severe cases, brown mucus can even be a sign of a lung abscess, which is a painful collection of pus that is usually caused by a bacterial infection.

Whatever the cause, brown phlegm should always prompt a visit to the GP, particularly if accompanied by a prolonged cough. 

White

White phlegm can be a sign of viral bronchitis and may progress into yellow-green mucus.

Gastro reflux can also cause people to cough up thick, white sputum.

As can COPD, which makes the airways narrow and the lungs produce an abnormal amount of mucus.

Congestive heart failure is another culprit, which occurs when the heart gradually loses its ability to pump blood around the body.

This causes fluid to build up in different areas, which may get coughed up as white sputum.

Black 

Black phlegm is often a sign of inhaling something like dust, which traditionally affected coal miners. 

However, it can also signal something more sinister, such as the rare fungal infection Exophiala dermatitidis, which can occur as a complication of cystic fibrosis.

Smoking cigarettes and crack has also been linked to black mucus. 

Clear

Clear phlegm helps keep the respiratory system moist and is usually a sign your body is healthy.

However, allergies like hayfever can increase it so its production becomes noticeable.

Viral infections like bronchitis and pneumonia also often start with excessive clear mucus production before the phlegm progresses to become yellow or green-stained.

Clear mucus production also naturally increases during the winter months to help warm up cold air so it is less harsh on the lungs.  

Red or pink

Red or pink phlegm is likely caused by blood and may be a sign of an advanced lung infection, like pneumonia or TB.

Congestive heart failure and a pulmonary embolism - blockage in the arteries in the lungs - can also be to blame.

In severe cases, red-tinged phlegm or even coughing up blood can be a sign of lung cancer.  

As well as producing the above, you should also see your GP if you have had a cough for more than three weeks, or are experiencing chest pain, unexplained weight loss or difficulty breathing.