Essential Oil Related Seizures (EORS): A Multi-Center Prospective Study

Background: Essential oils (EOs) like eucalyptus and camphor are known to have proconvulsant properties. These EOs are present in many over the counter balms and oils. In this study we evaluated the relationship between exposure to these EOs and the first episode of seizure and breakthrough seizures in known epileptic patients. Methods: This was a multi-center prospective study, conducted in four hospitals over four years. Every person presenting with the first episode of seizure or breakthrough seizure was asked about exposure to EOs, mode of exposure, time to onset of seizure in relationship to exposure, duration of seizure, type of seizure and antiepileptic drug therapy. All patients were followed up for recurrence either physically or telephonically for a minimum period of 6 months. Findings: During the four-year period there were 55 patients from four major hospitals who had essential oil related seizure (EORS). 22 had essential oil-induced seizures (EOIS) and 33 had essential oil-provoked seizures (EOPS). Male: Female ratio was 1:1, age ranged from 8 months -77 years. In EOIS group 95% had generalized onset motor tonic clonic seizures and 5% had focal onset impaired unawareness motor seizures while in EOPS group 43% had focal onset impaired awareness motor seizures, 28% generalized onset motor tonic clonic seizures, 14% focal to bilateral tonic clonic seizures and 15 % focal aware motor onset seizures. Essential oils implicated were preparations containing eucalyptus and camphor. Interpretation: Exposure to proconvulsant essential oils of eucalyptus and camphor are an important unrecognized cause of first seizure and breakthrough seizure. Essential oil related seizures can occur as de novo seizures (EOIS) or as breakthrough seizures (EOPS). Identifying the true causative factor will prevent unnecessary antiepileptic drug therapy and future recurrence. Funding Statement: No funding was received. Declaration of Interests: None of the authors has any conflict of interest to disclose. Ethics Approval Statement: Study was approved by the Institutional Review Board of the coordinating centers and informed consent was obtained from all the subjects.