Why your phlegm changes colour (and what it means)

Important Note: This article provides general health information and is not a substitute for professional medical advice. Always consult a qualified healthcare professional for diagnosis and treatment of any health condition.

Every time you breathe, your airways make a thin layer of mucus to trap dust, germs, and other particles. Most of the time, it’s thin and clear, so you swallow it without realising. However, when you’re unwell or have an underlying condition, your body can start producing more phlegm. 

Your phlegm might also become thicker or change colour as your immune system responds to infection or irritation. This change in colour can give you some insight into what’s happening in your body, but it can’t diagnose an illness on its own.

In this article, you’ll learn what your phlegm colour can mean, when to see a doctor, and simple ways to manage it at home.

What different phlegm colours can indicate

The colour of your phlegm can change for various reasons. While these clues can help you understand what’s happening, they’re not a diagnosis. Here’s what some common colours might suggest:

Clear phlegm is often normal

When your phlegm is clear, it's usually a sign that your respiratory system is working as it should. Healthy airways produce clear mucus to keep themselves moist and clean. 

Sometimes, a slightly increased amount of clear phlegm can be due to:

• Allergies: Your body might produce more clear mucus as a reaction to allergens like pollen or dust.
• Minor irritation: Exposure to very cold air or mild irritants can temporarily increase clear phlegm production.
• Bronchitis (early stage): In the very early stages of a viral bronchitis, you might notice clear phlegm before it changes colour.

White phlegm is a sign of congestion

White phlegm often means there's some level of congestion or inflammation in your airways. It can also be caused by post-nasal drip (mucus draining from the nose/sinuses into the throat).

It can become thicker and appear white from the following illnesses:

• Viral infections: Common colds or flu can cause white phlegm, especially in the early stages, as your body ramps up mucus production.
• Dehydration: If you're not drinking enough fluids, your mucus can become thicker and appear white.
• Asthma: People with asthma might produce white, thick phlegm, particularly if their airways are constricted.
• Gastroesophageal reflux disease (GERD): Acid reflux can sometimes irritate the throat and lead to increased white phlegm.

Yellow or green phlegm is often linked to infection

When phlegm turns yellow or green, it's usually a sign that your immune system is actively fighting an infection. The colour comes from white blood cells (neutrophils) and other waste products involved in the battle against germs. 

Common causes include:

• Common cold or flu: Many viral respiratory infections can lead to yellow or green phlegm as they progress.
• Bronchitis: This inflammation of the bronchial tubes, often caused by a virus, can result in yellow or green phlegm.
• Pneumonia: A more serious lung infection that can produce significant amounts of yellow or green phlegm.
• Sinusitis: An infection of the sinuses can cause post-nasal drip, leading to coloured phlegm in your throat.

These colours often appear with viral infections, not just bacterial ones. Viral infections are caused by viruses (like the common cold or flu) and usually clear up on their own, while bacterial infections are caused by bacteria and sometimes need antibiotics.

In Australia, most respiratory infections are viral and will get better with rest. A doctor can help determine whether antibiotics are actually needed.

Brown or black phlegm can indicate more serious concerns

Darker phlegm, such as brown or black, can be quite concerning and usually means there's something more significant happening. 

This might be due to:

• Smoking: Heavy smoking or exposure to secondhand smoke can cause tar and other particles to build up in the lungs, leading to brown or black phlegm.
• Pollution or dust exposure: Working in environments with high levels of dust, dirt, or smoke (like firefighters or miners) can lead to dark phlegm.
• Old blood: Sometimes, older blood from a previous nosebleed or a small bleed in the airways can appear brown in phlegm.
• Fungal infections: In rare cases, certain fungal infections can cause black phlegm.

Red or pink phlegm is a cause for concern

Any red or pink tint in your phlegm usually indicates the presence of blood. While sometimes it can be due to something minor, it always warrants attention.

Here are some of the common reasons you might have pink or red phlegm:

• Minor irritation: A forceful cough can sometimes irritate the delicate lining of your airways, causing a tiny bit of fresh blood that looks pink or streaky red.
• Bronchitis: Severe coughing from bronchitis can sometimes lead to small amounts of blood.
• Serious infections: Conditions like pneumonia or tuberculosis can cause bloody phlegm.
• Pulmonary embolism: A blood clot in the lung can cause sudden shortness of breath and bloody phlegm.
• Lung cancer: In some cases, bloody phlegm can be a sign of lung cancer, especially in smokers.

If you see red or pink phlegm, especially if it's persistent, a large amount, or accompanied by other worrying symptoms, you should seek medical attention promptly. 

Any amount of bloody phlegm should be assessed by a doctor, especially if persistent or associated with shortness of breath or weight loss.

When to see a doctor

While phlegm colour can be a useful indicator, it's not the only thing to consider. You should see a healthcare professional if you experience:

• If yellow, green, brown, or black phlegm lasts for more than a few days, especially if it's getting worse
• Any red or pink (bloody) phlegm, even small amounts, should be checked out
• Difficulty breathing or shortness of breath
• Chest pain
• High fever
• Night sweats or unexplained weight loss
• Wheezing or a new cough that won't go away
• If you generally feel very unwell or your symptoms are getting worse instead of better

For any of these symptoms, it’s best to speak with a doctor. You can book an online appointment through Updoc to speak with one of our AHPRA-registered Partner Doctors.

Important facts about phlegm

Phlegm is a normal part of how your body protects your lungs and airways. Understanding a few key facts can help you know what’s normal and when to pay attention.

• Phlegm is normal: Your body constantly produces mucus as a protective layer to keep your airways clean and healthy.
• Colour is only one clue: While phlegm colour can be helpful, it needs to be considered alongside your other symptoms, how long they’ve lasted, and your overall health.
• Hydration helps: Drinking plenty of fluids keeps mucus thinner and easier to clear from your airways.

Practical tips for managing phlegm at home

While it's crucial to see a doctor for concerning symptoms, here are some practical tips that can help manage phlegm at home:

• Drink plenty of fluids: Water, clear broths, and warm teas can help thin your mucus, making it easier to cough up and clear from your airways.
• Use a humidifier: A cool-mist humidifier in your room can add moisture to the air, which can help soothe irritated airways and loosen thick phlegm. Make sure to keep it clean.
• Avoid irritants: Stay away from cigarette smoke, strong fumes, and other airborne irritants that can make your phlegm worse.
• Rest: Giving your body time to recover is vital, especially when you're fighting an infection.
• Elevate your head: If phlegm is bothering you at night, try sleeping with your head slightly elevated using an extra pillow. This can help with drainage.

If you’re worried about your symptoms or your phlegm hasn’t improved, it’s best to speak with a doctor. You can book an online consultation with an AHPRA registered Partner Doctor through Updoc for quick professional advice and treatment options.

FAQs

Is phlegm always a bad sign?

No, clear phlegm is healthy and normal. Even white, yellow, or green phlegm can often be part of a common cold that will resolve on its own. It's when the colour is unusual, or other symptoms are severe or lasting, that it becomes more of a concern.

How can I get rid of phlegm?

You can help your body manage phlegm by staying hydrated, using a humidifier to keep the air moist, and avoiding irritants like smoke. 

Coughing is your body's way of clearing it, so it's generally good to let yourself cough it up. Your doctor might suggest specific medications if the phlegm is related to a particular illness.

Should I cough up phlegm or swallow it?

Generally, it's better to cough up phlegm rather than swallow it, especially if it's thick or coloured. This helps to clear your airways. 

If you do swallow it, it usually passes harmlessly through your digestive system, but coughing it up can make you feel more comfortable.

Important disclaimer

This article provides general health information based on trusted Australian guidelines and is intended for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. 

Always seek the advice of your general practitioner or another qualified healthcare provider with any questions you may have regarding a medical condition. Do not disregard professional medical advice or delay in seeking it because of something you have read in this article.