Why, when my leg/arm/any limb “goes to sleep” does it hurt once the feeling starts coming back to, but if I am given a numbing agent, it doesn’t hurt when the feeling comes back?

Question

So, when you fall asleep leaning on your arm and roll over, it starts to hurt as the feeling comes back. But if you go to the dentist and they numb your mouth, it doesn’t hurt once that starts coming back?

In: Biology

Answer 1

Physician here:

The pins and and needles you feel is due to the return of blood supply and electrical activity to your nerve endings happening all at once. With a nerve block there is no loss of blood supply, just a slow return of electrical activity as the drug wears off.