A patient requires antibiotics for a dental infection and has a documented penicillin allergy (mild rash). Which antibiotic is MOST appropriate to prescribe?

Correct answer: A. Cephalexin (first-generation cephalosporin)

• A. CORRECT. For mild penicillin allergy (rash, not anaphylaxis), first-generation cephalosporins (cephalexin) can be used safely in most patients. The cross-reactivity between penicillins and cephalosporins is <2% (not the historically cited 10%). For dental infections in penicillin-allergic patients with NON-SEVERE reactions, cephalexin is a reasonable and effective choice. For severe (anaphylactic) allergy, avoid cephalosporins and use clindamycin or azithromycin.
• B. Azithromycin (macrolide) is an alternative for penicillin-allergic patients but has increasing resistance among dental pathogens — it is a second-line option.
• C. Clindamycin is appropriate for SEVERE penicillin allergy (anaphylaxis/urticaria), but for mild reactions (simple rash), cephalexin is preferred for its broader spectrum against dental pathogens.
• D. Ciprofloxacin (fluoroquinolone) is not indicated for routine dental infections — it lacks activity against anaerobic oral bacteria and is reserved for gram-negative specific indications.