Cats do it. Dogs do it. Humans do it, too, often two times in a row.

Naturally, we’re talking about sneezing. So, why exactly do we sneeze?

You probably believe (or were taught) that we sneeze so that our noses can get rid of irritants. While this is true, it is only part of a much more complicated story as Michael Aranda explains in the video. But first, you need to know the nose.

Our nostrils and accompanying nasal passages are separated by a wall called the septum. Behind the nose is a space called the nasal cavity, which connects to the back of our throats, and this is surrounded by sinuses, a system of air-filled pockets. The sinuses are lined with a thin layer of tissue (a membrane) that makes mucus, generally known as snot. Mucus prevents germs, dirt, and pollen from getting into our lungs. On the surface of the cells of the mucous membrane are microscopic hairs called cilia, which move all together like waves to clear mucus from the sinuses. All of these parts are necessary to filter the air we breathe into our lungs.

However, as Aranda explains, a University of Pennsylvania study investigated sneezing and discovered the nose is very much like a temperamental computer, requiring a reboot from time to time. Watch his SciShow Quick Questions video here.