You swallow a litre of snot every day.

You swallow a litre of snot every day.

Your body produces snot (nasal mucus) for at least three reasons: 1) To trap particles of dust and other debris in the air you inhale. 2) To humidify the air entering your lungs. 3) To warm the air entering your lungs. Snot reproduces continuously throughout the day, and is swept to the back your mouth (the nasopharynx) by millions of microscopic (about 0.006 millimetres in length) hair-like structures called cilia.