Why does black licorice make your tongue numb?

The compound in licorice root that gives it its distinctive flavor is called glycyrrhizin. Glycyrrhizin is fifty times sweeter than sugar and belongs to a class of compounds called saponins. Saponins are surface-active agents that can cause foaming, just like soap. They can also interact with the receptors on the tongue that sense sweetness.

When you eat black licorice, the glycyrrhizin binds to these receptors and blocks them from being able to sense other flavors. This is why black licorice tastes so overwhelmingly sweet, and it also explains why it can make your tongue feel numb.

The numbing sensation is caused by the fact that glycyrrhizin interferes with the normal function of the nerves in your tongue. This can lead to a temporary loss of sensation, which is why your tongue may feel numb after eating black licorice.

The numbing effect of black licorice is not harmful, but it can be unpleasant for some people. If you don't like the way black licorice makes your tongue feel, you can avoid eating it.