Part 2: Toxicity—In Vivo Studies

In vivo studies are conducted by the scientific community using whole, living organisms. Because of ethical considerations, human studies are not widely used to collect toxicology data; instead, animal studies are most prevalent. Although animals and humans have many significant differences in their anatomy and physiologic processes, some species are similar enough that study data can be extrapolated to provide information about the substance’s toxicity in humans.

Occasionally, a human will accidentally or purposefully use a high dose of a substance, including essential oils. Although rare, these incidences can provide critical information about a substance’s toxic dose and toxicity symptoms. These isolated cases are commonly referred to as case studies. Below are summaries of two in vivo toxicology studies; one an animal study and the other, a human case study.

Animal Study:

A third party study (not by doTERRA) was conducted that measured the toxicity of fennel (Foeniculum vulgare) essential oil in rats. It was determined that the median lethal dose (LD50) of fennel essential oil was 1326 mg/kg. It is important to put this data in perspective when applying it to human consumption; this dose is equivalent to a 125 lb. or 57 kg adult consuming approximately 1,255 drops or five 15 mL bottles of fennel oil. At this high dose, animals exhibited symptoms such as sedation, respiratory distress, muscle weakness, muscle tremors, unresponsiveness, and death. Although not conclusive, this data provides insightful clues about the dose ranges of fennel essential oil that may be toxic in humans.

Case Study:

In one case, reported by a third party study, a four-year old boy was temporarily hospitalized after accidentally ingesting two teaspoons (equal to about 10 mL or 170 drops) of Tea Tree (Melaleuca alternifolia) essential oil. He displayed symptoms including ataxia, mental changes, and unresponsiveness. The boy received mild medical treatment and was held for observation. Within 24 hours of admittance to the hospital, the boy made a complete recovery and upon follow-up examination, reported no long-term effects. Obviously, the boy’s dosage far exceeded appropriate internal recommendations, and it was fortunately low enough that he was able to recover. Consuming a dose of this size is never recommended. This study tells us that up to two teaspoons or less of Tea Tree essential oil may be a toxic dose for a child and possibly toxic for an adult. Although they do not provide conclusive information, case studies can provide information about toxic doses and their symptoms while also demonstrating the importance of storing and using essential oils safely.

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