Certain essential oils have convulsant properties and have been associated with seizures for centuries, though everyday use of oils has generally been considered safe for the average person. But after conducting the largest-ever case study of essential oil-related seizures in adults, a group of Indian neurologists have found evidence suggesting their use may not be as safe as we previously assumed.
In a paper published March 26 in Epilepsy Research, patients at four South Indian hospitals who experienced a seizure were evaluated for their use of camphor and eucalyptus essential oils. Analyzing 350 seizure cases that spanned a four-year period, the researchers determined that 15.7%, or the seizures of 55 patients, may have been induced by the inhalation, ingestion or topical use of essential oils. After advising the patients to discontinue their use of the oils, they found that the vast majority of those patients did not experience another seizure during a follow-up period.
Thomas Mathew, a professor and the head of the neurology department at St. John's Medical College Hospital in Bengaluru, India, told The Academic Times that he and his colleagues noticed an uptick of seizures that may have been caused by the patient using essential oils, in people with epilepsy and a history of seizures, and in those without such a history. They realized that they had not previously been asking their patients with epilepsy about exposure to balms and oils containing convulsant essential oils, which led them to develop and conduct more formal research on eucalyptus and camphor oil specifically.
"There is literature linking essential oils and seizures, especially that of camphor and eucalyptus, and especially in the pediatric age group," Mathew said. "But there are only a few case reports in adults."
The researchers began asking non-epileptic patients who experienced their first seizure, and patients with epilepsy who experienced a breakthrough seizure, about their usage and exposure to the oils. A breakthrough seizure occurs suddenly after an epilepsy patient has not experienced a seizure for an extended period of time. Mathew called the initial results "surprising and shocking," as many patients reported using various balms, toothpastes, tablets and other items containing eucalyptus and camphor oil, which are popular in India for treating headaches, backaches and the common cold.
All over the world, essential oils are found in over-the-counter products for treating minor ailments. Their use has also grown as part of the health and wellness movement associated primarily with Western cultures, in personal care products for aromatherapy, stress relief and sleep aids. The global essential oils market has grown rapidly, reaching $17 billion in 2017 and projected to reach $27 billion by 2022, with Europe holding the largest share.
Of the 55 patients in the study who were determined to have had an essential oil-related seizure, 40% of them had never experienced a seizure before, so the researchers considered their seizure to be essential oil-induced. And 60% of them had a history of seizures, so their seizure was considered essential oil-provoked. The age of the patients ranged from 8 months to 77 years, though the majority were adults.
The patients were asked to stop their exposure to these essential oils and any products that contained them. The researchers then followed up with the patients for a period of 1-3 years to monitor any recurrence of seizures. All of the non-epileptic patients had been treated with anti-seizure medication for two to four weeks following their first seizure, and none of them had a recurrence of seizures after stopping their exposure to essential oils. And 94% of the epileptic patients also remained seizure-free during the follow-up period.
The authors emphasized in the paper that this is a topic that has not been well studied, and that it needs significantly more research, as essential oils are used all over the world. They noted that their observational study involved a small number of patients from one region in India, and they said their findings must be corroborated by larger, more diverse studies in the future.
"The essential oils appear to be provoking these seizures, but whether they are truly causative or associative must be clarified by further evidence from larger blinded studies," the authors reported. "However, despite these limitations, [this] is one of the largest studies on essential oil-related seizures in adults."
"[The] true incidence of these essential oil-related neurological disorders like seizures are difficult to ascertain as doctors rarely ask these in their history taking, as these are not mentioned in conventional textbooks or teaching curricula," said Mathew. "Also, many patients with seizures may not come to the neurologists or epileptologists in the tertiary care hospitals. We need large epidemiological studies to find the true prevalence, which is unfortunately not available at present."
Examples of the study participants were given in the paper, including a 29-year-old man who had no personal or family history of seizures. He inhaled steam from a mixture of eucalyptus oil and hot water to treat a cold, and five minutes into the inhalation he lost consciousness and experienced a seizure. As part of the study, he avoided exposure to essential oils and had no subsequent seizures during the following two years. A 27-year-old woman who was on medication for juvenile myoclonic epilepsy similarly experienced a seizure after inhaling a eucalyptus oil steam mixture. She also had no seizures for the next two years while avoiding the oils.
By cutting out the exposure to camphor and eucalyptus oils in any form, the researchers said they were able to reduce the number and dosage of antiepileptic medications for those with epilepsy. "Ingestion of eucalyptus and camphor has been reported to trigger seizures, while the topical application is generally perceived as safe. However, our observations from the current study indicate that this may not be true," the authors said in the paper.
Mathew and his co-authors suggested that physicians should inquire about the exposure to these essential oils in patients experiencing their first seizure and in those with breakthrough seizures, and seizure and epilepsy patients should be aware of potential side effects. The team is currently studying the effects of these essential oils on different diseases and disorders, and their early results suggest that many people are addicted to the oils and are using them without valid reasons.
"We think the findings of this study have implications across the globe, in all hyper-excitable neuropsychiatric disorders like epilepsy, migraine, cluster headache, anxiety disorders and addiction," Mathew said. "These are totally unexplored areas of medicine, toxicology and neurology."
The study, "Essential oil related seizures (EORS): A multi-center prospective study on essential oils and seizures in adults," published March 26 in Epilepsy Research, was authored by Thomas Mathew, Saji K John, Asha Shaji, Raghunandan Nadig, Sagar Badachi, Delon D Souza, Manjusha Therambil, G.R.K Sarma and Gareth J. Parry, St. John's Medical College Hospital; Vikram Kamath, Rakesh Jadav and Sreekanta Swamy, Apollo Hospital; Shiva Kumar R., Sakra World Hospital; and Gurucharan Adoor, Vydehi Institute of Medical Science.