What the colour of your phlegm REALLY means, according to doctors

It’s that time of year when the dreaded lurgy strikes more than ever, leaving millions of us with a hacking cough, full of snot and a sore throat.

That’s because Christmas is the peak time for viruses to spread, given how much socialising we do indoors.

And there’s plenty going around for us to catch: recent figures show a rise in seasonal viruses such as flu, the new Covid variant, whooping cough and norovirus.

Of course, coughing up phlegm and sneezing out snot is all part of battling a cold.

‘Phlegm is a deliberately sticky substance made by the body to trap matter – including germs from a virus – which is then expelled from the body by coughing it up,’ explains Dr Tom Jenkins, an NHS GP in Gloucestershire and founder of the cough and cold remedy Centoreze. ‘It’s a very clever mechanism.’

And as revolting as it seems, the colour of your phlegm can reveal important clues about your health.

From yellow to green and even black, read on to see what the different colours may mean – and how you can treat yourself.

CLEAR/WHITE PHLEGM

If you cough up white or clear phlegm it may mean you have upper respiratory tract infection such as a cold, or an allergy. 

This colour isn’t anything to worry about.

‘Phlegm can be caused by one of two mechanisms,’ says Dr Jenkins. ‘It can either come from your chest, or from your nasal passages. 

‘With the latter, mucus from your nasal passages has dripped down the back of your throat – known as post-nasal drip – into your chest, and your body is coughing it up as a protective mechanism. This tends to be clear sputum.

‘If you want to know which cause it is, sit on a chair and lean forward with your nose facing the ground for five minutes. If you stop coughing, it’s your nose that’s the problem, not your chest. But be aware the contents of your nose will probably drip on to the floor.’

YELLOW/GREEN PHLEGM

This indicates you most likely have a viral, but possibly a bacterial infection.

It could be in your sinuses and it’s dripping down your throat and into your chest. 

If it is green or brown it could however indicate an infection in your lower respiratory tract, if you are coughing it up from the lungs.

The dark green colour occurs when white blood cells rush in to fight infection.

‘In usually healthy people, yellow and green secretions with a cough are usually triggered by a viral infection,’ explains Dr Ash Husain, consultant chest physician at Spire Bushey Hospital in Hertfordshire. These infections do not need antibiotics.

‘In smokers with chronic lung disease, producing more than the usual amount of phlegm, with increased thickness, and a change in colour to yellow or green, suggests an infection, so see your doctor,’ he adds.

Also, if you feel quite unwell, have a fever and are coughing up a lot of discoloured phlegm, Dr Husain recommends you seek advice – especially if you have a long-term health problems such as asthma, emphysema, chronic bronchitis, or if the person affected is very young or elderly.

PINK/RED PHLEGM

This can be a sign you have fluid on the lungs (a condition called pulmonary oedema) – people suffering from this bring up a very distinctive frothy pink phlegm.

‘This is the most important colour in terms of concern,’ says Dr Husain.

‘If your phlegm is rusty or blood stained you should see a healthcare professional urgently.’

Bright red blood may be caused by coughing, or having a chest infection. It often happens in older people who smoke.

However a slight blood-staining of mucus isn’t usually a concern if you’ve got a cold or bronchitis.

It can be caused by irritation and inflammation and continual blowing of your nose.

If you don’t have a cold, however, then it’s wise to seek medical advice, especially if you have other symptoms such as persistent cough, weight loss or fever.

BROWN PHLEGM

You’re probably more likely to have this if you smoke, especially if you’re a heavy smoker.

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

It can also be triggered by air pollution and breathing in smoke from a fire.

Regularly produced brown coloured sputum with fever, breathlessness or chest pain should always be reported to your doctor, however, as with other symptoms, brown sputum may indicate an infection or other conditions.

BLACK PHLEGM

Black mucus 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 serious going on.

Although very rare, this could be fungal or bacterial pneumonia, or a lung disease associated with long-term inhalation of irritants and/or dust.

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

YELLOW OR GREEN PHLEGM FROM A COLD VIRUS? HERE’S HOW TO TREAT IT

While the vast majority of coughs and colds are caused by viruses – and therefore won’t be helped by antibiotics – there are other measures you can take to ease your symptoms and try to recover quicker, says Dr Jenkins.

One option is products such as Centoreze, which contains pelargonium – a traditional herbal remedy made from geranium root. Pelargonium is the only herbal medicine recommended by NICE – the National Institute for Health and Care Excellence – specifically for cough, and is also licensed by the MHRA (Medicines and Healthcare Products Regulatory Agency) to relieve symptoms of coughs, colds and sore throats in adults and children aged 12 and over.

Trials suggest it stops some types of cold and flu virus replicating by speeding up the rate at which the hairs in the nose move, helping to expel mucus.

‘It also blocks the landing sites that viruses and bacteria need to stick to cell walls,’ explains Dr Jenkins. ‘This means they are more easily brought up as mucus is cleared from the airways.’

Pelargonium also stimulates the action of immune cells that fight infection, such as white blood cells, and natural killer cells, that engulf and kill bacteria and viruses.

To dry out a runny nose that could be causing your cough, try an over-the-counter steroid nasal spray, which the NHS guidance suggests after discussion with a doctor or pharmacist.

Using a steroid nasal spray will reduce inflammation in the area and decrease mucus production – easing your nasal symptoms and cough.

If your nose is blocked, first take something to unblock it – a decongestant such as Sudafed or Otrivine, then something to wash out the mucus that’s in the way, either a salt water spray such as Sterimar or your own salt water nasal rinse (see below). Only once you’ve got rid of the mucus should you consider a steroid nasal spray – otherwise it’s just hitting the mucus and won’t act on the skin.

‘To make your own nasal salt rinse at home add ¼ level teaspoon of kitchen salt and ¼ level teaspoon of bicarbonate of soda (not baking soda) to ½ pint of lukewarm water, advises Dr Jenkins. ‘Put the glass lip to your nose rather than your mouth and ‘drink’ it through your nose. You’ll cough, swear, splutter and it’ll taste like you’ve had 10 packets of crisps – it’s ugly, but effective!’

Also, while ibuprofen can reduce aching and fever, never take codeine as that is a cough suppressant, warns Dr Jenkins. ‘Tempting as that may be, it’s not a good thing as it could mask a bacterial infection such as pneumonia.’