What Causes Greenish Phlegm?

  • 1st Revision: Maura Mary Joseph

When you feel the beginnings of a cough and you reach for a tissue,What do you see? What color sputum do you see? Most people are embarrassed to admit that they peek at their tissue. But what they don't know is that it can reveal important information about your health. If you have ever coughed up green phlegm, you may wonder what that means.

Green phlegm can be caused by many underlying health conditions such as bronchitis, cystic fibrosis, sinusitis, and pneumonia. Just because you have green phlegm it doesn’t give you a specific diagnosis but it does give you a clue to identifying the underlying health issue that ails you. 

What is phlegm?

Phlegm is a form of mucus that is produced in the lungs and chest. Your body produces phlegm as a defense mechanism, as it is reacting to an irritant of some kind and trying to get rid of it. It could be triggered by a bacterial infection, such as bronchitis, sinusitis, or pneumonia. It could be a viral infection like an upper respiratory infection. People who suffer from chronic lung diseases such as COPD, cystic fibrosis, or bronchiectasis may be more likely to have phlegm. In addition, environmental allergies and asthma are also affected by this factor.1

Colours of phlegm 

What does green phlegm mean

When white blood cells in the mucosa come into contact with an irritant or an infectious organism, their response is to produce enzymes that are designed to drive away the invaders. These enzymes contain iron, which is what makes the nasal discharge green. If the mucus sits around, it will get more concentrated, and as a result, it will have a more intense green color. This is the normal order of things, regardless of whether the offending agent is a virus (which is the most common cause of sinus infection) or a bacterium.2


Phlegm that is green in color is usually a sign that your body is attempting to fight off an infection. Phlegm may seem yellow at first, and then it may change to a green color as the infection worsens. The shift takes place depending on how severe the illness is and how long it lasts.3

Phlegm that is green in color is usually brought on by:

Sinusitis - This is also referred to as a sinus infection. Sinusitis can be caused by a number of different things, including viruses, allergies, and even bacteria. When bacteria is the cause of a sinus infection, you may see phlegm that is green or yellow, postnasal drip, congestion in your nasal passages, and pressure in your sinus cavities.3

Pneumonia - In most cases, this is a complication that develops from an underlying respiratory condition. People who have pneumonia may cough up phlegm that is green, yellow, or bloody red. The symptoms that you experience are going to be different depending on the type of pneumonia that you have. However, most forms of pneumonia have a number of common symptoms, including fever, chills, shortness of breath, and a cough.3 

Cystic fibrosis - This is a chronic condition of the lungs that causes mucus to accumulate in the lungs. This disease most commonly affects young adults and children. Cystic fibrosis can cause a range of different phlegm colors, ranging from brown to yellow to green.3

Bronchitis - A dry cough is usually the first symptom, followed by the production of phlegm that is either clear or white. You might start coughing up yellow and green mucus over time. This is a sign that the sickness may have progressed to the stage where it is now being caused by a secondary bacterial infection. Coughing might linger for up to three months.3


Phlegm does not pose a health risk by itself but, when it accumulates to excessive levels, it can obstruct the airways. Coughing is the most common way to release phlegm, and it is generally accompanied by symptoms such as sore throats, stuffy noses, and runny noses.4

Treatment for a green phlegm

Phlegm that comes with mild symptoms can be treated at home. You can try taking an over-the-counter cough suppressant (like dextromethorphan) and/or an exportant to help thin the mucus in your chest (such as guaifenesin). Make sure that you follow the instructions that are printed on the packaging.3 

If your symptoms are very severe or if they linger for an extended period of time, you should consult a medical professional. They can help you figure out why you have phlegm and what the best way is to treat it.3

Natural and home remedies

Gargle with warm salt water. When you have a sore throat, cold, or the flu, gargling with warm salt water can be quite helpful since it helps to wash out mucus and decrease inflammation. Just dissolve a teaspoon of salt in one cup of warm water, and then sip the solution without swallowing it. First, gargle with the water for fifteen to thirty seconds, and then spit the water out into the sink. You can repeat this as many times as you want.5

Drink water. When you have a cold, it is very important to make sure that you keep your body well-hydrated by drinking a lot of water and other fluids. Make sure that you are obtaining the appropriate amount of fluid for your body's requirements in order for it to recover and become healthy.5

Fix sleep position. Using more pillows to prop your head up as you sleep can make breathing easier and help remove mucus from your chest.6

Warm drinks. A sore throat can be soothed by drinking a warm drink made of honey and lemon.6

Suck on hard candies and cough drops. They could help relieve a dry cough and calm an itchy or scratchy throat and reduce phlegm in your throat.6 

When to seek medical attention?

If you see phlegm in your airways or throat, or if you start coughing it up and it is affecting your daily life, it's probably time to make an appointment with your doctor.7

If the color of your phlegm is clear, green, or yellow, you should wait a few days or weeks before booking an appointment with your doctor. You should continue to monitor all of your other symptoms to see if there are any new developments.7 If you notice any red, brown, or black phlegm, or if you have frothy sputum, you should schedule an appointment with your doctor as soon as possible. It's possible that this is a symptom of something more serious and should be treated as quickly as possible.7

It can be hard to tell by yourself what kind of lung problem you're having but a doctor can figure out what's wrong by doing a number of tests, like X-rays and sputum analysis.7 Contact your doctor if you don't know what's causing the change in color or if you have any other strange symptoms.7


Your respiratory system creates phlegm as a defense mechanism for your lungs. Phlegm helps keep your lungs healthy. It's possible that you don't even notice your phlegm if you don't have a pre-existing medical issue. You will only be able to cough it up if you are unwell or if you have a lung condition that is persistent. Phlegm can change colors during the course of an illness, going from clear to white to yellow to green. This is a natural occurrence. It is an indication that your immune system is working hard to restore your health. If you detect a change in color that lasts for more than three weeks and it is affecting your day-to-day life, you should arrange an appointment with your doctor as soon as possible.


  1. Parsons J. What does the color of phlegm mean? | Ohio State Medical Center [Internet]. wexnermedical.osu.edu. 2017 [cited 2022 Oct 6]. Available from: https://wexnermedical.osu.edu/blog/what-does-the-color-of-your-phlegm-mean
  2. H R. Don’t judge your mucus by its color - Harvard Health Blog [Internet]. Harvard Health Blog. 2016 [cited 2022 Oct 6]. Available from: https://www.health.harvard.edu/blog/dont-judge-your-mucus-by-its-color-201602089129
  3. buoy health. Coughing Up Green or Yellow Phlegm | Why Your Mucus Changes Color [Internet]. www.buoyhealth.com. 2018 [cited 2022 Oct 6]. Available from: https://www.buoyhealth.com/learn/coughing-up-green-or-yellow-phlegm#definition
  4. MedlinePlus. Sputum Culture: MedlinePlus Medical Test [Internet]. medlineplus.gov. 2021 [cited 2022 Oct 6]. Available from: https://medlineplus.gov/lab-tests/sputum-culture/
  5. Pacific Lutherian University. Home Remedies | Counseling, Health & Wellness Services [Internet]. Pacific Lutheran University. [cited 2022 Oct 6]. Available from: https://www.plu.edu/chws/health/what-to-do-when/home-remedies/
  6. NHS. Chest infection [Internet]. National Health Service. 2020 [cited 2022 Oct 6]. Available from: https://www.nhs.uk/conditions/chest-infection/
  7. NHS. Cough [Internet]. nhs.uk. 2017 [cited 2022 Oct 6]. Available from: https://www.nhs.uk/conditions/cough/
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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Hana Hailu

Master's degree, Brain Science, University of Glasgow

Hana Hailu is an accomplished academic with a strong foundation in the field of brain science and pharmacology. She is currently pursuing her Master's degree in Brain Science from the prestigious University of Glasgow (2021-2022). Prior to this, Hana earned her Bachelor of Applied Science (BASc) in Applied Pharmacology from Queen Margaret University, where she studied from September 2017 to September 2021. With her deep knowledge and dedication, Hana is poised to make significant contributions to the world of neuroscience and pharmacology.

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