Medically reviewed by Amelia MacIntyre, DO Mucus, a fluid in your upper respiratory system, is usually clear. But a number of health conditions can cause it to turn brown. Also known as brown ...

Your body makes phlegm, aka mucus, to sweep out harmful bacteria and allergens. The color of the phlegm can depend on the causes. Here are possible reasons why it’s brown.

Connor noted that brown mucus could be an indicator of bronchitis or pneumonia, which you’ll want to keep in mind ― especially if you have other symptoms like cough, fever and shortness of breath.

Mucus is natural. If your body makes too much of it, it might be a sign of a wide range of problems, including acid reflux, allergies, asthma, infections, or other conditions.

Whether your mucus is yellow, green, red, or brown, this expert advice will help you understand what each snot color means and when to call a doctor.

Your mucus color changes as your health does—here's what it means if it's yellow, brown, red, green, clear, watery, or thick.

It's cold and flu season, which means a lot of snotty noses. Cindy Gellner, M.D., a pediatrician at University of Utah Health, explains what the different shades of mucus means.

Phlegm is a type of mucus. Learn more about the differences between mucus and phlegm, how to treat excess mucus, and more.

Mucus is a sticky fluid that lines your lungs, throat, mouth, nose, and sinuses and helps to protect against various infections.

Brown You may not be as familiar with brown mucus, and that’s because it’s not as common as clear, yellow and green boogers.