What Colour Phlegm Needs Antibiotics?


Phlegm is a specific type of mucus originating from the lungs that commonly serves a protective purpose. It can adopt different thicknesses, amounts, or colours that often serve as an indication of how one’s body is fighting off an illness.

Antibiotics are medication that destroys or slows down the growth of bacteria thereby treating only bacterial infections. For this reason, they cannot be used to treat viral infections, which are associated with white, yellow, and green phlegm.

In turn, individuals experiencing any other colour of phlegm should consult with their GP or seek additional medical advice as this type of phlegm indicates that the individual may be suffering from something more serious that may require medication, such as antibiotics, to help the individual fight it off.

What is phlegm?

The body produces mucus, otherwise referred to as phlegm or sputum, in various body parts, including the upper respiratory tract and gastrointestinal tract. Consisting of mucins and other proteins, mucus serves a critical function in protecting, lubricating, and lining sensitive surfaces inside the body, as well as trapping and flushing out potentially threatening foreign matter.1 However, occasionally mucus is overproduced so the body attempts to remove this excess by coughing it up as sputum or phlegm. Here, phlegm refers to a specific type of mucus originating from the lungs and lower airways often in response to inflammation.

Produced by the mucus glands, and consisting of 90% water,2 phlegm is typically thin, clear and unnoticeable. Although, amongst other causes, when an individual has an infection or is fighting off a cold, they often experience thickened phlegm of different colours. In turn, changes in the colour, thickness, or quantity of phlegm serves as an indication of health status and health problems.

Colors of phlegm & effects of each colour

Phlegm comes in a variety of different colours which serve as an indication of what health condition or problem an individual may be suffering from.

Below are the different colours phlegm may take and possible reasons for this.

ColourEffect of Colour
ClearIndicative of typical, normal health. Produced by the respiratory tract, where it then gathers at the back of the throat before being swallowed.
WhiteIndicative of nasal congestion. Inflamed tissues in the congested nasal opening slows the passage of phlegm through the respiratory tract, therefore making it both thick and cloudy.
YellowIndicative that the body is starting to fight off the infection or inflammatory condition.
GreenIndicative of a widespread immune response to an infection (typically viral meaning the infectious agent operates and replicates inside living cells) or inflammatory condition.
PinkIndicative of pulmonary oedema (i.e., fluid on the lungs).
RedIndicative of an internal injury, lung cancer, or a pulmonary embolism (i.e., a blockage in one of the pulmonary arteries in the lungs by a blood clot) in need of immediate medical attention.
BrownIndicative of possible bleeding, smoking, or chronic infection, such as bronchitis (i.e., infection of the main airways of the lungs thereby causing inflammation and irritation).
BlackIndicative of the presence of a fungal infection, lung disease, a history of smoking, or other regularly inhaled substances.


There is a multitude of reasons why one’s body produces phlegm in excessive amounts in various textures and colours, these often include:

  • Asthma – Individuals with asthma have an increased airway sensitivity to allergens, such as pollen, dust, and air pollution. They possess a higher risk of respiratory infection (i.e., infectious parts of the body involved in and responsible for breathing). Consequently, this contributes to inflamed airways and elevated phlegm production
  • Cystic fibrosis – Cystic fibrosis is a genetic condition that causes thick and sticky mucus production,3 which can block one’s airways and cause breathing difficulties. Here, the thick mucus traps bacteria and other infectious agents and provides ideal conditions for their growth, thereby increasing the risk for lung infections
  • Smoking – Smoking increases the risk of various diseases, including lung cancer, chronic bronchitis (long-term inflammation of the breathing tubes), and chronic obstructive pulmonary disease (the umbrella term for a group of lung conditions that cause breathing difficulties). Here, excessive phlegm production may be due to cigarette smoke suppressing the protein, Bik, that causes the natural death of mucus-producing cells, therefore, leaving these cells active to continue elevated mucus production4  
  • Respiratory tract infections – Different colour phlegm serves as a signal for lower respiratory tract infections (RTIs) which are infections affecting the body parts involved in breathing, such as the sinuses, throat, airways, and lungs

Examples of different RTIs that may affect phlegm include:

  • COVID-19 – Commonly occurring dry cough (i.e., a cough that is tickly in nature but doesn’t produce any phlegm) aggravates breathing problems due to inflamed lungs and air passes which contribute to chest tightness.
  • Flu / Influenza – These forms of viral infections may cause an individual to have green or yellow phlegm as this indicates the white blood cells (the fighting cells of the body’s immune system) are working to fight off the infection.
  • Bronchitis – Refers to infection of the main airways of the lungs thereby causing inflammation, irritation and increase mucus production. This condition can be acute (i.e., lasting three weeks) or chronic (i.e., lasting at least 3 months) in nature, but individuals often expel clear, grey or greenish phlegm.
  • Pneumonia – A viral or bacterial infection that inflames the air sacs in the lungs. It causes a dry cough or a cough that produces thick phlegm of a yellow, green, brown, or blood-stained colour.

When to take antibiotics?

Antibiotics are medications that destroy or slow down the growth of bacteria by having white blood cells (the fighter cells of the body’s immune system) attack harmful bacteria.

As antibiotics work primarily against bacteria, they can only be used to treat bacterial infections and not viral infections, such as coughs, colds and flu. Instead, these viral infections must be fought off by the body’s immune system. Therefore, instead of medication, home remedies and plenty of rest provide your body with the best chance to fight off the infection.

It is vital to only take antibiotics when absolutely necessary due to antibiotic resistance, where germs no longer respond to the antibiotic designed to kill them.

Therefore, when one is seriously under the weather and is struggling to fight off this infection, referral to the doctors may be necessary. The doctors will then assess whether antibiotics are necessary and advise the best course of action.

List of antibiotics to take

​​Antibiotics work in unique ways, but they are either bactericidal or bacteriostatic in nature.5

  • Bactericidal antibiotics destroy the bacteria by interfering with the formation of the bacterial cell wall or its cell contents
  • Bacteriostatic antibiotics prevent bacteria from multiplying

Under these broad types, various classes of antibiotics exist depending on their chemical structure. Some commonly prescribed antibiotics include:

Antibiotic Class Examples of Generic Drugs 
PenicillinsAmoxicillin, co-amoxiclav, flucloxacillin, and phenoxymethylpenicillin
MacrolidesAzithromycin, clarithromycin, and erythromycin
FluoroquinolonesCiprofloxacin and levofloxacin
Urinary anti-infectivesNitrofurantoin

Treatment and home remedies

Extending beyond antibiotic treatment there are numerous home remedies and care for treating atypical phlegm. Broadly, people should get additional rest and stay hydrated, as well as try other measures at home inducing:

  • Humidifier – Helps moisten the air, promotes easier breathing, loosens phlegm and makes it easier to cough it up
  • Eucalyptus or peppermint oil – Helps reduce excess mucus by loosening it so it can be coughed out. This can be inhaled using a diffuser or by using a balm (e.g., Vicks VapoRub)
  • Stay hydrated and warm – Hydration loosens congestion and helps the mucus move, whilst staying warm soothes the respiratory system
  • Saltwater or saline solution – Helps clear out the nasal passage through gargling, nasal sprays or neti pots

Meanwhile, some medications the doctors may recommend include:6

  • Over-the-counter medication – Expectorants to help clear phlegm from the airway by reducing its thickness or stickiness. Examples include Robitussin or Benylin
  • Prescription-only medication – Mucolytics that break down the structure of the molecules that form mucus. Examples include carbocisteine and erdosteine  

When to seek medical attention?

An individual should seek medical attention if they think they have asthma, tuberculosis, bronchitis or pneumonia. Those with pre-existing breathing difficulties or conditions should seek medical care at the earliest opportunity to tackle the issue early and prevent later complications.

It is also best to seek medical attention for the following symptoms:

  • Severe or long-lasting cough
  • Traces of blood in their mucus
  • Concerns about any symptoms
  • Ongoing chest pain and/or breathing difficulties
  • A rapid heart rate


Mucus is an essential fluid widely produced around the body that serves a protective function. However, changes in the thickness, amount, or colour of one’s mucus may sometimes be a cause for concern as they could potentially indicate a larger health concern.

Whilst overproduction of mucus in the throat (i.e., phlegm) often results in minor, viral illnesses (such as a sore throat, cough and cold, or flu) that the body fights off on its own, some conditions (such as bronchitis and pneumonia) may require medical attention.

Overall, if an individual has breathing difficulties, is coughing up blood, or already suffers from pre-existing breathing conditions they should seek emergency medical attention. Additionally, a healthcare provider should be approached when symptoms are persistent, recurring, and accompanied by other concerning symptoms.


  1. All About That Mucus: How it keeps us healthy [Internet]. Science in the News. 2018 [cited 2022 Oct 26]. Available from: https://sitn.hms.harvard.edu/flash/2018/mucus-keeps-us-healthy/
  2. Mucus, our body’s silent defender | unc health talk [Internet]. 2019 [cited 2022 Oct 26]. Available from: https://healthtalk.unchealthcare.org/mucus-our-bodys-silent-defender/
  3. About cystic fibrosis | cystic fibrosis foundation [Internet]. [cited 2022 Oct 26]. Available from: https://www.cff.org/intro-cf/about-cystic-fibrosis
  4. Mebratu YA, Schwalm K, Smith KR, Schuyler M, Tesfaigzi Y. Cigarette smoke suppresses bik to cause epithelial cell hyperplasia and mucous cell metaplasia. Am J Respir Crit Care Med [Internet]. 2011 Jun 1 [cited 2022 Oct 26];183(11):1531–8. Available from: https://www.atsjournals.org/doi/10.1164/rccm.201011-1930OC
  5. Nemeth J, Oesch G, Kuster SP. Bacteriostatic versus bactericidal antibiotics for patients with serious bacterial infections: systematic review and meta-analysis. Journal of Antimicrobial Chemotherapy [Internet]. 2015 Feb 1 [cited 2022 Oct 26];70(2):382–95. Available from: https://academic.oup.com/jac/article-lookup/doi/10.1093/jac/dku379Mucolytics [Internet]. [cited 2022 Oct 26]. Available from: https://patient.info/chest-lungs/chronic-obstructive-pulmonary-disease-leaflet/mucolytics
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.

Get our health newsletter

Get daily health and wellness advice from our medical team.
Your privacy is important to us. Any information you provide to this website may be placed by us on our servers. If you do not agree do not provide the information.

Jaskirat Kanwal

Masters of Science – MSc, Applied Neuropsychology. University of Bristol, UK

Jaskirat currently works in pharmaceutical care and in the mental health sector. Given their extensive background in psychology, they’re currently seeking to undertake their DClinPsych. They hope to study further, and continue in academia and research, with hopes to ultimately become an HCPC registered clinical neuropsychologist.

Leave a Reply

Your email address will not be published. Required fields are marked *

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
Klarity / Managed Self Ltd
Alum House
5 Alum Chine Road
Westbourne Bournemouth BH4 8DT
VAT Number: 362 5758 74
Company Number: 10696687

Phone Number:

 +44 20 3239 9818