Q. i had a root canal wednesday. i take xanax. so i took 1 mg before the appt and told my dentist…i had nitrous o. with the root canal…I slept all day thusday and noticed my face was a little itchy…today friday…my face is red and burns and i feel like im getting whelps that itch on my face…could this be a drug interaction…even tho i had root canal wed?,