Coughing up brown phlegm: Causes, symptoms and when to see a GP 

Overview

Noticing brown phlegm when you cough can be worrying. In many cases, it’s your body clearing out old blood or pollutants like smoke or dust. In Australia, exposure to cigarette smoke, bushfires, and environmental irritants, especially in rural or construction areas, is a common trigger. Here’s what brown phlegm might mean, when to see your GP, and what you can do at home.

Is coughing up brown phlegm serious? 

Not always. Brown phlegm may result from minor irritants or could indicate a more serious issue, such as a lung infection. Sometimes, brown phlegm is just your lungs getting rid of debris, especially if you’re a smoker or have been exposed to smoke or pollution. But at times it can also signal an infection, inflammation, or even bleeding in the lungs.

What does brown phlegm mean?

Coughing up brown phlegm can stem from various factors—some mild and temporary, others more serious.

Mild or common causes

• Smoke or air pollution- common during bushfire season or in smokers

• Dust or workplace exposure- construction, farming, or mining jobs

• Dry throat or dehydration- can make mucus appear dark in colour

• Old blood- caused by a minor nosebleed or irritation in the respiratory tract

• Chronic bronchitis- common in habitual smokers

More serious causes

• Pneumonia- especially if accompanied by fever or chest pain

• Lung abscess- a collection of pus in the lung; mucus may smell bad

• Tuberculosis (TB)- a rare but serious infection; more common in high-risk groups (those with weakened immune systems)

• Chronic lung disease (e.g., COPD)- more common in smokers

• Lung cancer- rare, but possible if coughing up blood-streaked phlegm

Note: Brown phlegm isn’t always serious, especially if it is occasional or related to recent exposure to smoke or dust.

Causes

Common causes: 

• Smoking (active or passive)

• Bushfire or industrial smoke exposure

• Chronic bronchitis

• Environmental dust (e.g., construction sites, rural roads)

• Dehydration

Less common but possible causes:

• Lung abscess

• Tuberculosis

• Fungal lung infection

• Lung cancer

• Occupational lung disease (e.g., coal worker’s pneumoniosis)

Symptoms 

Mild symptoms: 

• Chest tightness

• Fatigue

• Wet cough

• Mucus that is brown in the morning and clears later in the day.

Red flag symptoms: 

• High fever or chills

• Chest pain

• Shortness of breath

• Foul-smelling mucus

• Coughing up blood (pink or red streaks)

• Unexplained weight loss

• Mucus lasting more than 10 days

Home remedies 

These remedies may help in mild cases only, but are not a replacement for medical care.

• Stay hydrated- Water helps thin mucus

• Avoid smoke- Don’t smoke and avoid smoky spaces

• Warm fluids- Warm tea or soup can help loosen mucus

• Use a humidifier- Moist air can ease your cough

• Get plenty of rest- Let your body rest and recover

If your symptoms worsen or last more than a few days, see your GP.

How doctors diagnose brown phlegm

Your GP will review your medical history and symptoms. They might recommend some tests, many of which are bulk-billed through Medicare.

Common tests:

• Chest X-ray or CT scan- helps detect infections, blockages, or masses.

• Sputum culture- tests your mucus for bacteria, viruses, or fungi.

• Blood tests- examine for signs of infection or inflammation

• Bronchoscopy- a camera test to look inside your lungs to detect tumours, infections, or blockages (done in hospital).

• Pulse oximetry- measures your oxygen levels.

What other colours of mucus mean

The mucous plays a vital role in trapping and clearing irritants from the respiratory system. While clear mucus is normal, colour changes can indicate infections, allergies, or other underlying conditions. Here is a quick guide to what different phlegm colours may suggest:  

Colour	What it may mean	When to see a doctor
Clear	Normal or mild allergy	Usually not serious
White	Cold, mild infection, or congestion	If lasting more than 10 days
Yellow	Immune response to infection	If symptoms worsen
Green	Possible bacterial infection	See GP if lasting more than 10 days
Brown	Smoke, dried blood, or infection	If persistent or recurring
Red/Pink	Blood in mucus	See GP urgently

 

Contact a doctor

Here’s a simple checklist to help you decide: See a GP if: 

• Brown mucus lasts more than 10 days

• You have a fever

• You see blood in the mucus

• The mucus smells foul

• You’re losing weight or often feel tired

Call 000 immediately if:

• You’re struggling to breathe

• You have severe chest pain

• You’re coughing up blood

Getting medical help online

If you’re concerned about persistent brown phlegm, a general practitioner can help determine the underlying cause and recommend treatment options. There’s no need to visit a clinic in person; telehealth consultations are accessible throughout Australia. With Hola Health, you can:

• Speak to an Australian-registered GP online

• Get prescriptions, medical certificates, or referrals without leaving home

• Access Medicare rebates (bulk-billed for eligible patients)

 

Conclusion

Coughing up brown phlegm can be upsetting, but it’s not always serious. Most of the time, your lungs are simply clearing away irritants such as smoke, dust, or old mucus. However, if it persists, worsens, or appears alongside symptoms like fever, chest pain, or blood, you should see a GP. Early check-ups can prevent severe problems.