Mucus: Causes of White, Yellow, Brown, Grey, Black Phlegm

Colors of Mucus  (Phlegm, Sputum)

Phlegm may be clear (white), yellow/green, brown, grey, black, pink, orange, containing red streaks, or frothy.

Phlegm is mucus (sputum) coughed up from the chest. It reveals inflammation in the respiratory organs below the vocal cords (voice box, windpipe, bronchi and lungs). From the color and density of phlegm, and accompanying symptoms, its cause may be suspected.

Clear or Thin White Mucus

Clear or cloudy (white), thin and translucent mucus means there is no (or not much) pus or blood in it. Causes of clear white phlegm include:

  • Acute viral bronchitis (chest cold) is inflammation of bronchi (airways between windpipe and lungs), sometimes affecting persons with common cold, influenza or other viral respiratory infection. Low-grade fever, runny nose, itchy throat, hoarseness, wheezing and initially dry and then productive cough with clear mucus may last from several days to several weeks. Mucus can, in some days, turn to yellow or green (1).
  • Acute bronchitis caused by irritant gases (environmental or occupational) resembles viral bronchitis but usually there is no fever.
  • Former smokers with chronic bronchitis may cough up white phlegm. White mucus in chronic bronchitis does not require antibiotic treatment (1).
  • Asthma

Thick White Mucus

Main causes of thick, non-translucent, white mucus:

  • Drinking milk or other thick drinks can make originally clear mucus thick. Milk may cover the back of the throat, but milk itself does not cause mucus.
  • In gastroesophageal reflux disease (GERD), gastric acid may back up from esophagus into the windpipe and throat. Burning stomach, chest (behind the breastbone), and throat, and coughing up white, thick, often frothy mucus are main symptoms. Often, white mucus is the only symptom in GERD.

Yellow and Green Mucus

Mucus is yellow, when it contains inflammatory cells, mainly leukocytes. Thin yellow mucus can result from any cause of inflammation of respiratory tract: infection, allergy, asthma, irritation.

Thick yellow mucus speaks for infection – viral or bacterial. It is a regular symptom in acute or chronic bronchitis or bacterial pneumonia.

Green mucus contains pus (white blood cells mixed with bacteria) and suggests serious bacterial infection. It may be produced in chronic bronchitis, acute bacterial bronchitis, bacterial pneumonia, atelectasis, cystic fibrosis.

Brown or Rusty Mucus

Brown mucus can be due to:

  • Chocolate, cocoa or other foods that stain mucus brown
  • Smoking – from resins and tars in smoke
  • Inhaling dust or smog
  • Infection, especially in chronic bronchitis
  • Blood, arising from the lungs, bronchi, windpipe or voice box

Grey Mucus

Grey mucus can be caused by air pollution , cigarette or marijuana smoking.

Black Mucus

Black mucus can be due to:

  • Smoking marijuana, cigarettes, cocaine or other substances. It is not possible to reliably say, if someone is smoking marijuana or cigarettes on the basis of the smoker mucus color. A smoker who has quit smoking may cough up mucus (black or other colors) for several days or weeks after quitting (4).
  • Air pollution
  • Coal workers pneumoconiosis or anthrosilicosis (black lung disease)
  • Fungal (mold) lung infection, like allergic broncopulmonary aspergillosis (ABPA), causing bronciectasis (3)
  • Old blood (5) from COPD (bronchitis or emphysema), tuberculosis, cancer or other bronchial or pulmonary disorder

NOTE 1: vomiting black liquid is a symptom of bleeding from the stomach and has to be checked by a doctor as soon as possible.

Blood in Mucus

Blood in mucus appears as red strikes, brown mesh or obviously red blood.

Pink Mucus

Pink mucus in asthma contains eosinophils (a type of white blood cells appearing in bronchial wall in certain allergies).

Frothy Mucus

Frothy mucus originates from lungs. In pneumonia or lung edema, fluid washes some surfactant (a substance that keeps lung vesicles dilated) from vesicular walls into inflammatory fluid and makes it frothy. Frothy mucus may be also caused by gastroesophageal reflux disease (GERD).

Related Articles:


  1. Acute bronchitis (
  2. White mucus in chronic bronchitis does not require antibiotic treatment (
  3. Allergy to molds (Aspergilus) and black mucus (
  4. Mucus after quitting smoking (
  5. Black mucus can be from old blood in the bronchi or lungs (
About Jan Modric (249 Articles)
Health writer

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  • Misti

    I think all the denial from the drug users is funny, I have been smoking marijuana for 20 yrs. Since I was 13, I am now 33, and when ever I have briefly quit, the black shit in my phlegm disappears, and as soon as I start up again, bingo! There it is again, I have just recently quit again (forever this time) and what do you know, the black shit has disappeared again, it’s a no brainer if you ask me, did you know one joint is equivalent in tar to 118 cigarettes? well there you go, just look at the black shit inside your bong or what comes out from the end of your joint, imagine what our poor lungs must look like