When we think of drug allergies, the drug that comes to mind most often is penicillin and its derivatives, such as amoxicillin. This is due in part to the fact that antibiotics are so widely prescribed, though allergy to penicillin ranges from 1-3% among adults.
    There are other classes of drugs used by dentists and oral surgeons prior to dental procedures or surgery that may cause allergic reactions, and these are anesthetics or pain reducing drugs referred to as “caines.” Lidocaine (brand name Xylocaine) is the most widely used “caine” in dental offices and is also commonly used in emergency rooms prior to suturing up skin cuts or deeper lacerations.
    Lidocaine can be purchased from different manufacturers, and can be purchased as pure lidocaine (with preservatives), or with the addition of epinephrine, a vasoconstricting drug used to prevent bleeding, prevent absorption of the lidocaine in the bloodstream, and concentrate the lidocaine in the tissue for better pain reduction. The difference is that dentists and oral surgeons tend to purchase lidocaine with epinephrine, while emergency rooms usually stock lidocaine without epinephrine.
    Like all drug allergic reactions, reactions to lidocaine can be mild with immediate local tissue swelling, itching, trouble swallowing, or severe with generalized hives, trouble breathing, and changes in heart rate and blood pressure. It may not be the lidocaine causing the reaction, but the epinephrine or preservatives that are also present in the preparation.
    In all lidocaine reactions, patients should be referred to an allergist for evaluation, and a sample of the lidocaine preparation purchased and used by the dentist or emergency room should be taken to the allergist for study and testing.
    Following a history and physical examination, an allergist will make dilutions of the lidocaine and test the patient by both prick (skin puncture) and intradermal (skin injection) methods. If the testing is all negative, then a full strength intradermal injection will be given. If no local reaction occurs, then the patient is not allergic and may use lidocaine again, during a dental procedure or surgery.  In addition, if the patient gave any history that he/she had symptoms any number of hours after leaving the dentist’s office or emergency room, then the patient will need to return in 24 hours to the allergist for evaluation. This is to rule out any “delayed” drug reaction. Thus, the testing used to rule out a “caine” allergy is safe and reliable, and can help your dentist determine the best course of action needed for your dental care.