Phlegm is a mucus-like substance produced by your lungs and respiratory system. When you get sick with a cold or a sinus infection, your body will produce more mucus than normal in an attempt to trap and expel the virus or bacteria causing your illness.

Depending on your illness, the color and consistency of your phlegm will change. The American Chemical Society recently released a video that describes what different colors of phlegm may indicate and offers tips about which treatments are best for your symptoms.

  • Yellow or white phlegm is present when you’re congested. The color, combined with the thickness of your phlegm, indicates that you could have a cold.
  • Green phlegm indicates the presence of neutrophils (a type of white blood cell) and a green-colored enzyme that they produce, called myeloperoxidase. Green phlegm indicates that your body is likely hard at work fighting a viral infection.
  • Red phlegm indicates the presence of blood in your mucus and is generally the result of irritation and drying of your nasal tissue. A little bit of blood is nothing to worry about, but if you experience excessive bleeding, contact your doctor right away.

For more information on phlegm or for advice on treatment methods, contact your health professional.