The colour of your phlegm could reveal what’s going on with your health

Coughing up phlegm may appear a sign of more serious illness. But it’s important to understand why phlegm appears.

Viral coughs take longer to clear than many people realise, according to NHS GP Dr Tom Jenkins. He advised: “In young healthy people, 50 percent will clear over 10 days and 90 percent will clear over 25 days.”

Around seven million courses of antibiotics are prescribed each year for viral cough and cold symptoms as people flock to their GP wanting to alleviate symptoms.

While symptoms can be distressing and antibiotics can kill bacteria, it’s not effective in treating a virus.

“This is usually totally unnecessary, said Dr Jenkins. “All it does is add to the huge and growing problem of antimicrobial resistance caused by antibiotic overuse.

“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 and the colour of phlegm can indicate the cause of your infection.”

Mucus protect us said Dr Jenkins. He 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.”

There are measures you can take at home to ease symptoms and try to recover quicker, said Dr Jenkins.

The GP has just launched a new over the counter cough and cold medicine called Centoreze.

The product contains pelargonium, a traditional herbal remedy made from geranium root.

Pelargonium is the only herbal medicine recommended by the National Institute for Health and Care Excellence (NICE) specifically for coughs, and it is also licensed by the Medicines and Healthcare Products Regulatory Agency (MHRA) 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,” explained Dr Jenkins. “This means they are more easily brought up as mucus is cleared from the airways.”

But Dr Jenkins notes you should always check with your GP before taking herbal or other medicines alongside prescription drugs.

What does different colour phlegm mean?

Dr Jenkins offered advice on what different colours can mean.


The presence of Green sputum signifies the presence of white cells to fight an infection present; the white cells produce an enzyme which turns the sputum green.

Dr Jenkins said: “Sometimes green sputum can be produced first thing in the morning only, but production of regular green sputum through the day is a symptom that should be discussed with your GP as it can sometimes signify a bacterial infection.”


This can be a sign that you have fluid on the lungs (pulmonary oedoema). Dr Jenkins said: “People with acute pulmonary oedoema bring up a very distinctive frothy pink phlegm.”


Red phlegm or mucus is the most important colour in terms of concern. Dr Jenkins said: “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 more sinister conditions. If your phlegm is rusty or blood stained, you should see a health care professional urgently.”


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

Dr Jenkins 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. Burn sputum can also signify a bacterial infection and should be discussed with your GP.”


Black mucus can be caused by breathing in dark-coloured dirt or dust. Dr Jenkins said: “Smoking can also cause black streaks in your mucus.”

Other things to remember

As a general rule, the darker the phlegm, the more likely you are to have something a bit more serious going on, said Dr Jenkins.

He added: “Your first step should be to see your GP. A cough without phlegm, fever or breathlessness is more likely to be viral acute bronchitis, which will also not respond to antibiotics in the majority of cases.

“If you’ve had a cough for more than three weeks, always see your GP to consider long-term and sinister conditions, including lung cancer.”

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