If you have dental work done, make sure your dentist doesn't use injections that contain vasoconstrictors. Epinephrine is added to prolong numbing, however it is a vasoconstrictor which can damage your nerves. I have no proof, this is what happened to me, but I wish I could go back in time and ask my dentist to use Mepivacaine or Carbocaine. Those two medicines do not contain vasoconstrictors.