What colour is your phlegm? What white or yellow mucus could be signalling

Coughing up phlegm or sneezing out green snot is par for the course when you’re battling a cold. But revolting as they are, these gooey substances do reveal important clues about your health. Dr Sarah Brewer, Medical Director for Healthspan, says both can provide tell-tale signs of how well your body is coping with a cold or respiratory infection.

“The fact that you have a runny nose or are coughing up phlegm shows your body is fighting off infection and, hopefully, eliminating it from your body,” says Dr Brewer.

“Secondly, the colour of your phlegm can reveal how serious your infection is, and if it’s very discoloured or blood-stained, it’s wise to seek medical advice.”

Mucus actually protects us, said Dr Brewer. She explained: “It does this by keeping our lungs, airways and nasal passages moist, and by carrying antibodies and immune cells, which help fight off infection.”

So what can different colours of mucus and phlegm signal?


Clear mucus means that the tissues in your nose have swollen up, so that the mucus in your nose can’t move through your nasal passages as quickly as usual, according to Dr Brewer.

She added: “It becomes thicker, gloopy, and cloudy because of low moisture levels. If you cough up white phlegm it may mean that you have an upper respiratory tract infection, or congested sinuses.”

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Yellow mucus and phlegm that has a thick consistency and is quite dark may mean you have a viral or bacterial infection.

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This could be in your sinuses, or in your lower respiratory tract, advised Dr Brewer.

“The dark yellow, and even green, colour happens when white blood cells rush in to fight infection.”


Pink phlegm can be a sign you have fluid on the lungs (pulmonary oedema).

Dr Brewer said: “People with acute pulmonary oedema bring up a very distinctive frothy pink phlegm.”


Red phlegm or mucus is the most important colour in terms of concern.

Dr Brewer warned: “If you cough up small amounts of bright red blood. It may be caused by coughing, having a chest infection or, sometimes, is a sign of a lung tumour.

“If your phlegm is rusty or blood stained, you should see healthcare professional urgently.

“If you cough up small amounts of bright red blood, it’s probably from your lungs.

“It may be caused by coughing or having a chest infection. It often happens in older people who smoke.”



You’re probably more likely to have brown phlegm and mucus if you smoke, advised Dr Brewer, especially if you’re a heavy smoker.

She said: “Brown coloured mucus can be caused by dried blood from nose bleeds, having a cold, or picking your nose.

“Brown mucus can also come from air pollution and breathing in smoke from a fire.”


Black mucus and phlegm can be caused by breathing in dark-coloured dirt or dust.

Smoking can also cause black streaks in your mucus.

“As a general rule, the darker the phlegm, the more likely you are to have something a bit more serious going on,” explained Dr Brewer.

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In this case, your first step should be to see your GP.

Treating a cold and flu

Good intakes of vitamins A, E, and D  are linked to fewer respiratory complaints according to a new study published this week in the journal BMJ Nutrition Prevention & Health. These results add to the growing body of evidence of the importance of good nutrition in supporting immune health.

While nutrition appears to play a role in reducing the risk of several infections, exactly how it boosts immunity is very complex and is still not fully understood.

According to Rob Hobson, Registered Nutritionist at Healthspan: “Many nutrients are involved in maintaining a healthy immune system and protecting against the respiratory conditions to which we are more susceptible to during the winter months.

“It’s important right now that everyone is getting the optimum amount of nutrients, they require to support a healthy immune system so while people are slow to make dietary changes, supplementation could be a prudent option.  Taking a multivitamin and mineral supplement on a daily basis is a cost-effective way to bridge any gaps that exist in your diet.”

While diet should always come first, it is difficult to get enough vitamin D unless you regularly eat oily fish and fortified foods. Also, in our northern climate, we are unable to make sufficient vitamin D in our skin at this time of year. That’s why official guidelines recommend that everyone takes a daily vitamin D supplement all year round

In light of the COVID19 pandemic, an article in the Irish Medical Journal suggested that adults take 20mcg to 50mcg supplements per day to help reduce the severity of infection.

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You can try Healthspan’s new ImmunoVit Super C and Vegan D Plus (120 tablets, £11.95,


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