What Does the Color of Your Phlegm Mean

Phlegm color can tell you a lot about your health

While “phlegm” isn’t the prettiest word — or substance, for that matter — it can tell you a lot about your respiratory health.

Your phlegm can change color for a variety of reasons, such as infection, allergies or other underlying health conditions. And hue changes in your phlegm can be a valid reason to speak to your doctor.

“The color of your phlegm can offer clues about what might be happening in your body,” says Danielle McGovern, DO, a family medicine physician at Geisinger. “Importantly, you can observe any changes in color quickly and easily, and when you consider those along with other symptoms, you can decide if you need to seek medical attention.”

What is phlegm?

The body uses mucus to trap germs and contaminants as your immune system’s first line of defense. Many parts of the body produce mucus, like the GI tract, throat, nose, sinuses, mouth and more.

Phlegm is a thick, sticky mucus produced by the respiratory tract that protects against germs and foreign contaminants like pollution from entering your airways.

“Clear phlegm is normal. It’s made of water, salt and immune system cells,” says Dr. McGovern. “When you become sick, the phlegm may thicken as well as change color as your body fights off the infection.”

What does the color of your phlegm mean?

Phlegm can come in nearly all shades of the rainbow, and each color may indicate different underlying conditions that range from harmless to more serious concerns.

Find out what some colors of phlegm might be telling you:

White phlegm

White phlegm is normally no cause for alarm. It indicates sinus activity and nasal congestion due to allergies, asthma or maybe the early stages of a respiratory infection like a cold. As the airway passages get inflamed and mucus production increases, phlegm in the respiratory tract can thicken and become white.

Yellow phlegm

Yellow phlegm is a sign your body is fighting off a mild viral or bacterial infection.

“White blood cells are responsible for fighting infections, and as they get picked up in the mucus, they can cause it to turn a yellowish hue,” says Dr. McGovern. “In many cases, getting plenty of rest and fluids can resolve the issue.”

Green phlegm

Cough up green phlegm? That’s an indication your body is fighting off a more serious infection like bronchitis or pneumonia. Your mucus may go from yellow to green due to the higher concentration of white blood cells.

While green phlegm may be alarming, it’s a natural byproduct of the immune system activity necessary to fight off the infection. Consider seeing your doctor if other symptoms are getting worse or your phlegm discoloration continues.

Red phlegm

Pink or red phlegm can be a more serious warning sign. Pink or red indicates bleeding in your respiratory tract or lungs.

Hard coughing can cause bleeding by breaking the blood vessels in the lungs and lead to red phlegm. However, more serious conditions can also cause pink or red phlegm.

If your phlegm looks pink or red, talk to a physician soon.

“As a one-time symptom, it may not really be an issue, but if persistent, it might signal conditions like tuberculosis, a pulmonary embolism or, in some cases, cancer,” says Dr. McGovern. “Check if your other symptoms might indicate something serious, and always err on the side of safety.”

Brown phlegm

Brown phlegm can also be a warning sign because it signals past bleeding. As the blood ages, it turns brown.

Typically, brown phlegm is a sign of a chronic lung condition like cystic fibrosis or COPD (chronic obstructive pulmonary disease). If you notice brown phlegm, you should see your doctor.

Black phlegm

Black phlegm is cause for immediate action — especially for people with compromised immune systems — because it likely means a fungal infection. You should see your doctor right away.

Is phlegm color a good health indicator?

Monitoring changes in your phlegm color and assessing your other symptoms can tell you a lot about your health — and help you determine whether to call your doctor.

But while phlegm color can give you hints about what’s going on inside your body, it’s not a definitive diagnosis.

“Phlegm discoloration is only part of the story,” says Dr. McGovern. “Just because your phlegm is white or yellow doesn’t mean you have a clean bill of health. Phlegm color is a reference point that needs to be considered along with other symptoms. If you have any reason to think your condition is worsening, or if your symptoms become severe, like persistent fever or chest pain, talk to your doctor.”