Brain injury due to anaphylactic shock as a result of formocresol used during root canal treatment

AIM: Formocresol is still used in many parts of the world despite concerns over its toxicity. A case of a 45-year-old women who experienced brain injury after an analyphlactic reaction to formocresol is presented. SUMMARY: During routine root canal treatment, the patient experienced nausea and vomiting after formocresol was used as an antibacterial agent in the pulp chamber. The procedure was discontinued and the symptoms resolved. Four days later, the treatment was continued by a different dentist, and the patient developed anaphylactic shock within 10 min of placement of a formocresol-soaked cotton pellet. She received emergency medical treatment and magnetic resonance imaging (MRI) revealed brain injury characterized by swelling of the gyrus in the cerebral watershed territory of the left parietal-occipital lobe. The patient subsequently made a full recovery after supportive treatment. KEY LEARNING POINTS: A type-I allergic reaction can be induced by formocresol. The reasons for the brain injury are thought to be cerebral hypoxia, which was induced by the anaphylactic shock and/or cerebral parenchymal oedema. All dentists should be aware of the risks involved in the use of formocresol and avoid using materials containing formocresol and related agents.