![Reactions show](https://d3dthqtvwic6y7.cloudfront.net/podcast-covers/000/017/747/small/bytesize-science.jpg)
Summary: It’s peak cold and flu season, and mucus is making many of our lives miserable. But despite being a little icky, phlegm gets a bad rap. This germ-fighting goo contains cells and chemical compounds that help us power through a cold. You can also think of mucus as a traffic light for your health — what turns up in our used tissues can be a useful clue about the inner workings of our immune systems.