With their ability to block pain signals to the brain, local anesthetics (LAs) have made possible many surgical procedures and interventions once thought impossible. LAs are generally safe and well tolerated when used correctly by trained professionals. However, adverse reactions do occur, and may generate a referral to an Allergist for evaluation of LA allergy. LA structure, classification, and metabolism will be briefly reviewed. A critical analysis of the studies and case reports involving LA allergy found via PubMed search for "local anesthetic allergy" and "local anesthetic hypersensitivity" will be discussed. In addition, the clinical evaluation of a patient with concern for a LA allergy will be examined.