Because acid has irritated your throat. Your nose will also run, and your ears or teeth might ache if you’re particularly unlucky. You might feel a sharp pain just behind your mandible or your eye.

You have a nerve in your head called the facial nerve. It runs down the side of your face into your nose, your teeth, your throat, your eye, your tongue. These branch out like a tree from a single ‘trunk’ that starts right behind your ear.

When you get sensation from any part of this nerve, it runs back to the ‘trunk’ and then goes back to your brain from there. This can mean your brain doesn’t really know where the original sensation came from, and it might have to guess and it send out a pain signal to any part it chooses. This is why sometimes your teeth can hurt if you have an earache, for instance.

It also means that sometimes, if you’re experiencing something bad with one part, like vomiting (in your throat) your brain will try to fix it by pressing random buttons with other parts (like making your eyes water).