Phlegm Color: What It Means & Common Causes

Phlegm color can change based on what is happening in the respiratory system, such as allergies, colds, or the flu. It is often clear or white, but other colors can appear as the illness progresses.

Changes in phlegm color, such as yellow, green, or pink, can be linked to infections like sinusitis or pneumonia, or even more serious conditions. In some cases, phlegm may contain blood, which can indicate inflammation or more severe lung problems.

Each phlegm color can suggest a different cause and may occur along with symptoms such as fever, wheezing, or shortness of breath. Treatment depends on the underlying condition and may involve medications, drinking plenty of fluids, or seeking medical care if warning signs appear.

What each color means

The different phlegm colors and their possible causes are:

1. Green or yellow phlegm

These colors usually appear when neutrophils are present in the airways. Neutrophils are defense cells that produce a green protein that dissolves in phlegm, and the color can vary depending on the amount of this protein.

This type of phlegm may indicate an infection in the respiratory tract or sinuses, such as sinusitis or pneumonia.

What to do: See a primary care provider or a pulmonologist so they can determine what type of infection is causing the phlegm and start the appropriate treatment.

2. Bloody or red phlegm

Blood in phlegm can be caused by several conditions, from pneumonia or sinusitis to more serious problems, such as tuberculosis or lung cancer.

According to the CDC, coughing up blood or sputum (phlegm) can be a symptom of active tuberculosis, especially when accompanied by symptoms such as cough, chest pain, fever, weight loss, or night sweats.

What to do: You should see a pulmonologist for diagnostic tests, such as a chest X-ray and sputum culture, to identify the problem and start the right treatment. Treatment will vary depending on the diagnosis made by the doctor. Blood in phlegm is a warning sign and should always be assessed by a doctor.

3. White or gray phlegm

White phlegm usually indicates inflammation in the upper airways, most often caused by viral infections that typically do not require antibiotics. The flu and sinusitis can also lead to this type of phlegm.

In rarer cases, this color may also happen after eating a lot of dairy products, as milk products can make phlegm thicker and give it a whitish color when it is coughed up.

What to do: You should drink about 2 liters of water per day to help loosen and clear phlegm. If your symptoms do not improve, see a primary care provider so you can receive the appropriate treatment for the condition causing the phlegm.

In the case of flu, treatment is usually focused on relieving symptoms. A healthcare provider may recommend medications such as acetaminophen or ibuprofen to reduce fever and discomfort.

Sinusitis may also be treated this way, but a doctor may recommend corticosteroids or, in some cases, antibiotics depending on whether the infection is viral or bacterial. In these cases, keeping the upper airways hydrated with saline nasal irrigation is very important to help clear mucus and relieve symptoms.

4. Brown or black phlegm

Smokers and people who work in heavily polluted environments, such as mines or construction sites, often produce brown or black phlegm because particles like tar and dust stick to the airways. As with smokers, this can make the mucus appear darker in color.

What to do: It is recommended to avoid places with a lot of dust or pollution and to stop smoking, if this applies.

5. Pink phlegm

Coughing up pink phlegm may be a sign of fluid in the lungs. According to the American Heart Association, heart failure can cause fluid to leak into the lungs, which may lead to a persistent cough or wheezing with white or pink, blood-tinged mucus.

What to do: In this case, it is important to see a pulmonologist or cardiologist to adjust treatment for the condition causing pink phlegm. In cases of heart disease, treatment may include specific medications.

6. Clear phlegm

Clear phlegm may be caused by inflammation in the respiratory system, such as allergic rhinitis, the flu, or a cold.

What to do: A healthcare provider may recommend treatments such as antihistamines, fever reducers, anti-inflammatory medicines, antibiotics, or pain relievers, depending on what is causing the clear phlegm. They may also suggest respiratory therapy sessions and, in some cases, oxygen therapy.

Changes in consistency

Normal, healthy phlegm is usually thin and more liquid. This type of phlegm is easier to clear and less likely to interfere with breathing. However, phlegm can become thicker in situations such as:

• Being in a very dry environment, such as an air-conditioned room

• Not drinking enough water during the day

• Having a respiratory allergy to pollen or dust, for example

• Taking medications that can dry out secretions, such as antidepressants, antihistamines, or decongestants

It can also become thicker during the flu or a cold, or in other infections, because the body works harder to eliminate viruses and bacteria and uses more water, which can dry out the mucus.

To help clear thick phlegm, it is important to drink about 2 liters of water per day and use nebulization with water or saline solution, as this helps thin the secretions and makes them easier to clear.