Phlegm is a type of mucus produced in your lower respiratory system; it’s that gelatin-like, sticky substance you cough up when you’re sick. Not all phlegm is made equally, though. Phlegm can present in different colors, amounts, and difficulty of which it can be expelled.

Phlegm & Mucus 101
Sometimes it’s easy for us to cough up the mucus that’s caught in our respiratory tract, and sometimes it seems stuck in our chests, causing discomfort.
Phlegm can often be harmless. It can be a reaction to allergies or air pollutants. Mucus in our bodies protects our cells and the lining of our respiratory system against bacteria, fungi, and viruses. It’s not necessarily a bad thing.
When to Worry
When your phlegm starts to turn colors or becomes excessive, it’s time to take notice. If you’re coughing up phlegm regularly, it’s time to see a doctor.