Coughing up phlegm is usually the result of a cold, a respiratory infection or a lung condition. The phlegm comes from the windpipe or lungs and is also called sputum. In general, the complaint resolves on its own. Persistently producing a lot of phlegm or a clear change in the phlegm sometimes requires further investigation.

What is mucus?

The mucous membranes lining the airways constantly produce a thin layer of mucus. This mucus keeps the airways moist and traps particles such as dust and bacteria. Tiny cilia move the mucus towards the throat. You usually swallow it without noticing.

When the airways are irritated or inflamed, they produce more mucus. The mucus is sometimes thicker and stickier. This means it remains more easily in the airways and triggers the urge to cough to clear it.

What is sputum?

Sputum is mucus that comes up from the windpipe or lungs and exits through the mouth. Sputum is therefore different from nasal mucus. Nasal mucus forms in the nose and sinuses, whereas sputum comes from the lower airways.

Coughing helps remove excess mucus from the airways. It is a natural cleaning response of the body.

What does coughed-up mucus look like?

The amount, colour and thickness of sputum vary from person to person and by cause. For example, the mucus may be:

Clear or white.
Yellow or green.
Thin and watery.
Thick, sticky or tacky.
Frothy.
Mixed with a small amount of blood.

Clear or white mucus fits with normal mucus production or mild irritation of the airways. Yellow or green sputum occurs, among other things, with inflammation. Colour alone does not tell whether bacteria or viruses are the cause. Green mucus therefore does not automatically mean that antibiotics are needed. A small amount of blood sometimes results from damage to a small blood vessel after forceful or prolonged coughing. Coughing up a large amount of blood always requires contacting a doctor (GP).

Possible causes of coughing up mucus

Common cold or respiratory infection

A viral infection is a common cause of coughing up mucus. The mucous membranes become irritated and produce extra mucus. There are often other symptoms too, such as a sore throat, a blocked nose, tiredness or a mild fever.

Acute bronchitis

In acute bronchitis the larger airways are inflamed. Frequent coughing and bringing up mucus are prominent. In addition, a wheeze, breathlessness, tiredness or a burning sensation behind the breastbone sometimes occur. Most symptoms ease within a few weeks. The cough may persist longer.

Pneumonia

A pneumonia causes coughing with thick yellow or green mucus. Other possible symptoms are fever, shortness of breath, chest pain, shivering and severe tiredness. Symptoms may start suddenly, but can also develop gradually.

Asthma

In asthma the airways are hypersensitive and regularly inflamed. This leads, among other things, to coughing, breathlessness, a wheeze and extra mucus. The severity of the symptoms often fluctuates.

COPD

People with COPD (chronic obstructive pulmonary disease) have long-term problems with coughing and mucus. Sputum often comes up regularly in the morning. During a flare-up (exacerbation) the coughing, the amount of mucus and the breathlessness suddenly increase.

Smoking and other irritants

Tobacco smoke damages the cilia in the airways and stimulates mucus production. This makes mucus remain longer. Vaping, air pollution, dust and chemical fumes also irritate the airways.

Bronchiectasis

In bronchiectasis, parts of the airways are permanently widened and damaged. This makes mucus more likely to remain behind. People with this condition cough up larger amounts of sputum every day and regularly have respiratory infections.

What helps with stubborn mucus?

Drinking enough keeps the mucous membranes moist. Regularly drinking water or tea sometimes makes thick mucus easier to cough up. Moving and changing position regularly support the clearance of mucus.

Try to avoid smoke, dust and strong smells as much as possible. Also ensure plenty of fresh air indoors. Smoking and second-hand smoke irritate the airways and increase mucus production.

Cough up the mucus gently when it loosens. Frequent, forceful coughing irritates the airways and can actually trigger more coughing. In long-term airway or lung conditions, a physiotherapist may teach breathing or coughing techniques to clear mucus more effectively.

When to contact the GP?

Contact the GP if you have:

Blood in the coughed-up mucus.
Increasing breathlessness or shortness of breath.
Chest pain.
High fever or persistent fever.
Drowsiness, confusion or signs of severe illness.
A cough that lasts longer than a few weeks.
Repeated episodes with a lot of sputum.
A clear and persistent change in the amount, colour or thickness of the mucus.
Unexplained weight loss.
A long-standing productive cough in someone who smokes or used to smoke.

Call your GP or the emergency number immediately in case of severe breathlessness, rapid deterioration or coughing up a larger amount of blood.

Examination

The GP will ask about the duration of the symptoms, the amount of mucus and any accompanying symptoms. The doctor will then usually listen to the lungs.

Depending on the symptoms, further tests are sometimes done. These may include a lung function test, blood tests, a chest X-ray or analysis of the sputum. In sputum testing, a laboratory looks, for example, for the presence of bacteria or other pathogens.

Treatment

Treatment depends on the cause. A viral infection usually gets better on its own. Rest, drinking enough and avoiding smoke support recovery.

In asthma or COPD, medicines aim to reduce inflammation and open the airways. Antibiotics only help with certain bacterial infections and are not needed for most respiratory infections.

With a persistent build-up of mucus, special breathing and coughing techniques can sometimes help. A physiotherapist teaches you how to clear the mucus from the airways with as little effort as possible.

Coughing up phlegm