Why redheads need more local anesthesia

redheadAs dental students we have done it hundreds of times already: local anesthesia. It’s may be the only procedure we have 100% confidence in completing. It’s like July 4th fireworks going off in dental brains because the patient’s “lip feels huge” and it is time to start the procedure. Yet, on a rare occasion, when we go through the normal routine with the appropriate dosage of anesthesia, they still have sensation. What gives?