What is the MOST common cause of true allergic reaction encountered in the dental office?

Correct answer: A. Antibiotics, particularly penicillins

• A. CORRECT. ANTIBIOTICS — above all the PENICILLINS — are the most frequent cause of genuine drug allergy in dentistry and the leading cause of drug-induced anaphylaxis. Beta-lactams act as haptens, binding host proteins to form immunogenic complexes that provoke IgE-mediated responses in sensitized individuals. (Worth noting: LATEX is the other major dental allergen, and it is often the true culprit when an 'anesthetic allergy' is investigated.)
• B. Analgesic reactions occur, but true allergy is far less common than to antibiotics. Most reported NSAID reactions are pharmacological intolerance (bronchospasm, gastric upset) rather than IgE-mediated allergy.
• C. True amalgam allergy is genuinely rare. Localized LICHENOID contact reactions to amalgam do occur on mucosa in direct contact with a restoration, but these are delayed hypersensitivity reactions, not the common systemic allergy.
• D. Composite resin allergy is uncommon in patients. Contact dermatitis to methacrylates is more of an OCCUPATIONAL hazard for dental personnel, which is why uncured resin should never be handled directly.

Note: Important clinical point: true allergy to AMIDE local anesthetics is exceedingly rare. Most reported 'anesthetic allergies' turn out to be vasovagal syncope, an epinephrine response, intravascular injection, or allergy to a preservative — the sulfite antioxidant in vasoconstrictor-containing cartridges, or latex in the cartridge diaphragm.