Question: Why do things taste different after eating certain other things? e.g Why does orange juice taste so bad after brushing your teeth?

Josh Meyers answered on 16 Jun 2015:

This is because two different kinds of taste receptors are active at the same time and your brain has decided that this is a bad combination.

So in this specific case orange juice is acidic and bitter, whilst toothpaste is sweet and cold (there is a cold taste receptor called CMR1).

So what you need to do is find a palette cleanser to remove the residual toothpaste before you drink your orange juice.

Problem solved.