Is It Better To Spit or Swallow Phlegm?

Have you ever felt something sticking to the back of your throat that feels a little ticklish and uncomfortable, especially when you have a cold? This sticky thing is called phlegm and is initially produced as mucus by mucous glands and goblet cells and eventually accumulates in the airway.1 Although irritating, phlegm actually helps trap and remove foreign particles and pathogens from our respiratory system.

However, what if there are potentially harmful substances in your phlegm? For example, when you have a cold and there could be a virus in your phlegm, should you spit it out or swallow it?

The short answer is, either is fine. This is because our stomach produces stomach acid that digests the pathogens in phlegm, making it harmless to the body. 

Phlegm can be removed by cells that ‘sweep’ it up the airway and down the throat, sometimes without you even knowing. However, in certain health conditions, excessive phlegm is produced and is not effectively cleared, causing it to accumulate in the throat, which could lead to some irritation. Read on to find out which health conditions cause excessive phlegm production and how you can remove phlegm more effectively!

Where do you get phlegm?


In some health conditions, such as asthma, chronic bronchitis, cystic fibrosis and infections of the respiratory system, phlegm accumulates because the mechanisms to clear mucus become ineffective.2 Patients with these conditions often have inflammation in their respiratory systems, which leads to increased phlegm production.

Lifestyle and environmental factors such as smoking and exposure to pollutants are also some of the main causes of phlegm production. Cigarette smoke can damage the hair-like structures, known as cilia, that remove phlegm from the airway and can cause phlegm to accumulate. This is why smokers often have a chronic cough due to irritation from the phlegm. The addictive component of cigarettes, nicotine, also causes an increase in the production of thick phlegm which is hard to remove.3


People with allergies develop symptoms of allergic reactions because their immune system ‘overreacts’ when they are exposed to certain foreign particles (called allergens), such as pollen, dust mites, certain foods, drugs, animal fur, and insect stings. These allergens are recognised as harmful substances by the antibodies and immune cells in an allergic person. The activated immune cells release chemicals, such as histamine, which can cause cells in the airway to increase phlegm production.4

Untreated allergies can also cause sinusitis, which is the inflammation of the sinuses. Sinuses are cavities located at the back of the eyes, cheeks, and forehead. There are cells within the sinuses which produce mucus, which drains from the sinuses to the nose and throat through connecting tubes. When sinuses are inflamed, more mucus is produced, and you might feel it flowing down your throat. This condition is known as post-nasal drip and it can also result in more phlegm production. 

What does phlegm feel like?

Phlegm often irritates the throat and can make you feel like coughing. This is because phlegm may stimulate the receptors and nerves in the throat. Coughing can help to remove the phlegm from your throat more effectively. Infections and inflammation can make phlegm thicker and stickier, which causes it to be harder to remove.   

Normally, phlegm is clear in healthy people. When there is an infection or inflammation, the phlegm may have other colours depending on the proteins and foreign substances that it could contain: 

  • Off-white and opaque phlegm - this could be often a symptom of a common cold. You should pay extra attention if you have asthma or other inflammations affecting the respiratory system, because whitish or off-white phlegm may mean that your condition is not well controlled.
  • Yellowish or greenish phlegm - this may be due to conditions such as bronchitis, chronic obstructive pulmonary disease (COPD), and viral or bacterial infections.
  • Reddish phlegm or phlegm with a hint of blood - some infections and smoking can cause bloody phlegm. It is recommended to seek medical advice if you have bloody phlegm as it could also be a sign of cancer.
  • Brownish phlegm - this could be due to smoking. But, if you do not smoke and are coughing up brown phlegm, it could be a symptom of pneumonia.

Effects of swallowing phlegm

According to an interview with Men’s Health, Dr Brett Comer explains that it is harmless to swallow phlegm because it will be broken down once it reaches the stomach. The stomach produces acid that digests the phlegm and the foreign particles or pathogens that it has trapped, which can then be removed from the body through excretion. 

How to avoid having phlegm?

If you smoke, it is strongly recommended that you quit. Besides the fact that some cigarette components can cause more phlegm to be produced, smoking also increases the risks for respiratory diseases, such as COPD, which can also increase phlegm production.

Since a common cold and respiratory infections cause excess phlegm production, you can avoid this by protecting yourself against these infections. The most effective way to do this is by maintaining good personal hygiene. 

It is also important to stay hydrated so that the phlegm produced can be naturally cleared without it sticking to the throat and causing any discomfort.

Treatment and home remedies

If you have phlegm and are looking for some home remedies, here are some simple and effective things that you can try:

  • Drinking more warm water - this makes your phlegm moist and less sticky so that it can be removed by clearing your throat or coughing more easily.
  • Taking a warm steamy shower or having steam therapy.
  • Using a humidifier - it moistens the air you breathe and can help in hydrating and clearing your phlegm. 
  • Using eucalyptus oil - eucalyptus oil can reduce inflammation and make phlegm less thick to allow removal.5
  • Gargling salt water - this helps to relieve your sore throat and discomfort caused by phlegm. 

If your phlegm is making it difficult to breathe, you should visit your GP for a consultation. Your GP may prescribe you expectorants to help loosen the phlegm by coughing. Be sure to ask your GP if you can use expectorants alongside other medication you may be taking. If you have asthma, it is important that you seek medical attention as more phlegm than normal, intense coughs and breathlessness can lead to an asthma attack.6 


Phlegm has an important function in protecting our body by keeping foreign substances out of our respiratory system. However, if there is excessive phlegm, it can become uncomfortable and irritating. If you have underlying conditions that are causing excessive phlegm production, like COPD or asthma, you should visit your GP who might prescribe you expectorants to help relieve your condition. There are also effective home remedies that you can try to help reduce the irritation caused by phlegm. 


  1. Farzan S. Cough and sputum production. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations [Internet]. 3rd ed. Boston: Butterworths; 1990 [cited 2022 Sep 28]. Available from: 
  2. Chilvers MA, O’Callaghan C. Local mucociliary defence mechanisms. Paediatric Respiratory Reviews [Internet]. 2000 Mar [cited 2022 Sep 28];1(1):27–34. Available from: 
  3. Chen EY, Sun A, Chen CS, Mintz AJ, Chin WC. Nicotine alters mucin rheological properties. Am J Physiol Lung Cell Mol Physiol [Internet]. 2014 Jul 15 [cited 2022 Sep 30];307(2):L149–57. Available from: 
  4. Thangam EB, Jemima EA, Singh H, Baig MS, Khan M, Mathias CB, et al. The role of histamine and histamine receptors in mast cell-mediated allergy and inflammation: the hunt for new therapeutic targets. Frontiers in Immunology [Internet]. 2018 [cited 2022 Sep 29];9. Available from: 
  5. Fischer J, Dethlefsen U. Efficacy of cineole in patients suffering from acute bronchitis: a placebo-controlled double-blind trial. Cough [Internet]. 2013 Nov 21 [cited 2022 Oct 3];9:25. Available from: 
  6. Evans CM, Kim K, Tuvim MJ, Dickey BF. Mucus hypersecretion in asthma: causes and effects. Current Opinion in Pulmonary Medicine [Internet]. 2009 [cited 2022 Nov 8]; 15(1):4–11. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Pei Yin Chai

Bachelor of Science - BS, BSc(Hons) Neuroscience, The University of Manchester, England

Pei Yin (Joyce) is a recent neuroscience degree graduate from the University of Manchester. As an introvert, she often finds it easier to express herself in written words than in speech, that's when she began to have an interest in writing. She has 2 years of experience in content-creating, and has produced content ranging from scientific articles to educational comic and animation. She is currently working towards getting a career in medical writing or project management in the science communication field.

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