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What are the Most Common Causes of Black Phlegm?

By Christina Edwards
Updated Mar 03, 2024
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Phlegm is the mucus that is expelled from the body during a cough or sneeze. Phlegm can come in a few colors, and the color of a person's phlegm often indicates his state of health. Black phlegm can be harmless, but it can also indicate a serious health problem. Some of the more common causes of black phlegm include mucus being tainted by particles of food or dust. Other, more serious, causes of black phlegm include smoke inhalation and certain diseases or infections.

One of the most common causes of black phlegm, especially in children, is ingesting something black or dark. Certain foods, such as chocolate or licorice, can turn a person's phlegm dark or black. Tiny particles of these foods can stick to the mucus in the throat when a person eats, and can produce black phlegm when he coughs or clears his throat.

Dirt and dust particles can do the same thing. If a person inhales dust while cleaning on a dusty day, or working in a garden on a windy day, small particles can get stuck in the mucus and be expelled. Although the color of the black phlegm can be alarming, this usually does not indicate a serious medical problem.

Another common cause of black phlegm is smoke inhalation. While cigarette smoke usually produces yellow or brown phlegm, very heavy smokers sometimes cough up black phlegm. People who smoke other drugs, such as crack cocaine or marijuana, are more likely to produce black phlegm than cigarette smokers.

Inhaling smoke from a large fire, like a house fire, can also cause a person's phlegm to turn black. This can indicate a serious medical problem. People who have recently been in or near a large fire with thick black smoke and begin to cough up black phlegm are advised to seek medical attention as soon as possible. Firefighters are especially susceptible to these types of respiratory problems.

It is also not uncommon for men and women who work in certain types of mines, especially coal mines and beryllium mines, to cough up black phlegm. This is often known as black lung disease, or coal worker's pneumoconiosis. After a prolonged exposure to the dust in coal mines, coal dust often builds up in a person's lungs, causing a chronic cough and shortness of breath. The risks of contracting this disease can be greatly diminished by wearing a respirator or other type of mask while working in a coal mine.

There are a also a couple rare fungal infections that can cause a person to cough up black phlegm. Aspergillosis and mucormycosis, which are caused by a fungus found in rotting plants, are two rare types of fungal infections of the lungs that humans can contract. Blood from these infections along with other infections of the lungs, including cancer and emphysema, can turn a person's phlegm dark, making it appear black.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon989168 — On Feb 22, 2015

I am a smoker, but never smoke more than 12 a day. I don't smoke pre-rolled cigarettes, I use rolling tobacco and filters. Usually I do not cough up that often. Recently I have been fighting off the cold again, and I cough up all the time. I am concerned as have been coughing up all sorts of different colors of mucus, including black/brown and sometimes with tiny traces of blood. All I have found on-line is that apparently it's "normal" for smokers to have this issue, but if non-smokers experience same thing they is cause for concern. Is it not possible that I am a smoker AND there's something wrong? My lungs collapsed in an accident six years ago, so it could be more than just a side-effect of smoking.

By anon960310 — On Jul 10, 2014

I have been coughing up this black phlegm. I've stopped the weed and this black phlegm is still here. Can you help me?

By anon959762 — On Jul 06, 2014

I am getting black mucus when I blow my nose. I am not a smoker.

By anon949868 — On May 07, 2014

I am getting black spots when I spit (when I have a cold), but not always. It usually gets back to normal once I am fine. Why is it so?

By anon939954 — On Mar 16, 2014

I've got the same thing. It's like a grainy black (ash like) substance in my phlegm (scary how dark it is!).

By anon333133 — On May 03, 2013

Whenever I do breathing exercises in the morning, then on the same afternoon, I have this black phlegm problem. Does it mean I'm breathing bad air? (I'm exercising inside my room itself).

By anon321283 — On Feb 21, 2013

I am ill and have been in bed three days. I am weak and my ribs hurt (although I am not coughing that much really as it hurts too much!)

I am a non-smoker but do have insulin dependent diabetes and quite a few other medical things wrong with me! I coughed up earlier a load of discolored phlegm but for the first time noticed black threads in it. Then when I coughed again it wasn't much, but a definite pinkish tone to the sputum! I am also asthmatic but am only 55 and just need to know I'm OK? I have had two pneumonia jabs so I know it's not that. I also have the flu jab every year. Help me!

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