Your respiratory system is protected by a special type of mucus, known as phlegm. Its job is to protect the lungs from stuff that could get in there, like dust, pollen or smoke. The stuff that makes it to your nose is called nasal mucus, or snot.
Nasal mucus is sticky like fly paper, trapping nasty stuff and flushing it away. How does it work normally, and why does it seem to go into overload when you have a cold? In fact, why is a cold called a cold? James May explains all.
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