Allergic diseases of the skin and drug allergies – 2033. Metronidazole skin testing associated with systemic reaction

Background Type I hypersensitivity reaction to metronidazole and its skin testing are rarely reported. A 69 year old lady had laproscopic cholecystectomy on 27September 2010. Post surgery, IV ciprofloxacin 400mg and metronidazole 500mg were infused at 8.00 pm. Within 30 minutes, she experienced pruritus and noted erythema on her left forearm followed by urticaria over upper limbs and chest. She reported mild shortness of breath and dizziness. There was no hypotension or angioedema. This was her first such reaction to drugs. Both antibiotics were stopped and IV hydrocortisone and oral chlorpheniramine prescribed. She was referred to our allergy service for suspected allergy to either ciprofloxacin or metronidazole. On assessment, she had received antibiotics on several occasions in the past and had reacted to ceftriaxone with pruritic maculopapular rashes. She had consumed metronidazole in June 2009 and ciprofloxacin in June 2009 and July 2010. A clinical diagnosis of Type I allergy to metronidazole was made.