What plants cause numbeness?

i am looking into plants that cause numbness and pain relief and i cant find any that do so i find plants that help people afflicted with numbness but none that induce it or an effect that reduces pain that can be ingested and not just applied over the skin i would like to find said plant and work it into a gum if possible is that possible so say i chew said gum it would provide pain relief over a long period of time as it releases the "toxins" ( i imagine they are toxins as in smaller animals this could put them off eating the plant)