Problems in the lungs can cause phlegm to change color. Green or yellow phlegm can occur with an infection, but brown phlegm might indicate bleeding in the lungs.

Phlegm is a type of mucus that comes from the lungs and respiratory tract. Typically, phlegm is clear, thin, and unnoticeable. When someone has a cold or infection, the phlegm can become thickened and change color. Other underlying causes may also affect phlegm color.

This article looks at the various colors that phlegm can be and what these mean for a person’s health. It also examines the different textures of phlegm and explains what someone can do if their phlegm changes.

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The color of phlegm can offer useful information about what may be happening with the lungs and other organs of the respiratory system. A person can follow this color guide for reference:


Clear phlegm is typical. It consists of water, salts, antibodies, and other immune system cells. After its production in the respiratory tract, most of it goes down the back of the throat, before a person swallows it.

Brown and black

Brown phlegm may indicate possible bleeding. While it is likely due to bleeding that happened a while ago, it can also indicate a chronic infection such as bronchiectasis. People living with cystic fibrosis may have brown phlegm, and individuals who smoke may also have brown phlegm.

Black phlegm may indicate the presence of a fungal infection, a history of smoking, or other substances that a person has inhaled regularly.

Someone who has black phlegm should contact their doctor immediately, especially if they have a weakened immune system.


White phlegm signifies nasal congestion. When the nasal cavity is congested, the tissues are swollen and inflamed, which slows the passage of phlegm through the respiratory tract. When this happens, the phlegm becomes thicker and cloudy or white. As such, white phlegm may occur due to allergies, asthma and often viral infections


Yellow phlegm suggests that immune cells are starting to work at the site of the infection or another type of inflammatory condition.

White blood cells are the cells of the immune system that are responsible for fighting germs. As they continue to fight the infection, the phlegm picks them up, giving it a yellowish tinge.


Green phlegm indicates a widespread and robust immune response. The white blood cells, germs, and other cells and proteins that the body produces during the immune response give the phlegm its green color.

While phlegm of this color can point to an infection, a person does not always need antibiotics. Most infections that lead to green phlegm are viral and usually resolve without treatment within a few weeks.

The phlegm often changes back to white after a few days. If this does not occur over a prolonged time, this may indicate a bacterial infection.

A person should consult with their doctor before using antibiotics. Using antibiotics when they are unnecessary can be harmful, as bacteria can build up resistance. If green phlegm occurs with breathing difficulties, chest pain, or coughing up blood, this is another sign to consult a doctor urgently.


Red phlegm signals the presence of blood. Doctors may refer to coughing up blood as hemoptysis. There are many reasons for blood in the phlegm.

A lot of coughing, such as with a respiratory infection, can sometimes cause small blood vessels in the lungs or airways to break and bleed.

When there is swelling in a person’s nasal passage, they can get a nosebleed. This can cause blood to seep into postnasal drip that they then cough out.

In other situations, blood in the mucus can indicate the presence of a serious medical condition such as tuberculosis, an abscess, or lung cancer.

Read on to learn more about blood in phlegm.

Phlegm can also take on different textures, ranging from watery to thick and tacky. Thin and watery phlegm is usually typical and indicates a healthy respiratory tract.

During an infection, immune cells, germs, and debris build up in the phlegm, making it thicker, stickier, and cloudier.

Coughing and sneezing help the body clear out the excess phlegm, mucus, and other things that do not belong in the respiratory tract.

Illness or infection are not the only things that can cause phlegm to become thicker. Being dehydrated or even sleeping can cause the phlegm to move slower and become thicker than usual.

Pink and frothy phlegm can mean that someone is experiencing heart failure, especially when it occurs with any of the following symptoms:

  • shortness of breath
  • sweating
  • chest pain

Anyone experiencing these symptoms should visit the emergency room immediately.

In addition, frothy phlegm can occur due to altitude sickness and acute respiratory distress syndrome.

It is important to note that doctors cannot diagnose a particular disease or condition according to the color of a person’s phlegm.

Having green, yellow, or thickened phlegm does not always indicate the presence of an infection. And if there is an infection, the color of the phlegm does not determine whether a virus, bacterium, or pathogen has caused it. Simple allergies can also cause changes in the color of the mucus.

Antibiotics will not always resolve green mucus.

People who have white, yellow, or green mucus that is present for more than a few days, or if they experience other symptoms, such as fever, chills, a cough, or sinus pain, should speak with a doctor. However, a person is usually fine to wait a few days to try and treat the symptoms at home before making an appointment.

Someone who develops new or increased red, brown, black, or frothy sputum should call their doctor for an appointment immediately. These symptoms can be signs of a more serious medical condition that requires prompt treatment.

White, yellow, or green phlegm is usually treatable at home.

People should try to get lots of rest and stay hydrated. Dehydration can worsen thick phlegm, making it harder to cough up. Some individuals may find that gentle walking can help them cough up the excess phlegm.

Some other measures to try at home include using the following:


Running a humidifier can help moisten the air, which eases breathing, making it easier to cough and loosen up the phlegm stuck in the chest.


OTC expectorants, such as guaifenesin, help thin the mucus, making it easier to cough up.

Expectorants are available for both children and adults at the local pharmacy. It is important to read the directions and take the medication exactly as the label or pharmacist instructs.


Gargling with salt water or using a saline solution to clear out the nasal passages is a common way to help clear out phlegm during a viral or bacterial infection.

For gargling, a person can dissolve a one-quarter teaspoon of salt in a cup of warm water. For clearing out the nasal passage, they can purchase a nasal spray or use a neti pot to rinse the nose.

Read on to learn more about home remedies for clearing phlegm.

In most cases, home care measures are safe and effective ways to deal with atypical phlegm.

It is important to call a doctor if the phlegm does not improve after a few days. An antibiotic may be necessary to treat an underlying bacterial infection.

Anyone with pink, red, brown, black, or frothy mucus should contact their doctor or go to the local emergency room for an evaluation.

Here are some common questions and answers regarding phlegm.

What is the difference between mucus and phlegm?

Different areas of the body, including the upper respiratory tract — which includes the nose, mouth, and throat — and gastrointestinal tract secrete mucus.

But phlegm refers to mucus that the lungs specifically produce. Another term for phlegm is sputum. So when a person coughs out mucus, people refer to it as phlegm, but not the mucus that the nose produces.

Is snot the same as phlegm?

Snot refers to nasal mucus, so it is not phlegm or sputum, which comes from the lungs.

What is the difference between phlegm from allergies and phlegm from a cold?

Allergy-related phlegm will tend to be clear. Colds or infections will usually cause green or yellow phlegm.

What do different colors of phlegm mean?

Different colors of phlegm can indicate different health conditions. White phlegm usually means nasal congestion, while yellow or green phlegm can indicate an infection. A person with cystic fibrosis may have brown phlegm, while black phlegm may suggest a fungal infection. Red phlegm can indicate the presence of blood.

What kind of phlegm should I worry about?

A person should seek immediate medical attention if they have red, black, or brown phlegm, as they can indicate the presence of blood or a potentially serious infection. If a person consistently experiences other colors of phlegm, it is important to contact a doctor for advice on suitable treatments.

What kind of phlegm is infection?

Yellow or green phlegm can indicate an infection. Black phlegm can also indicate a fungal infection.

Learn more on colds versus allergies and reasons for coughing up phlegm without feeling ill.

Read this article in Spanish.