I belong to several massage therapy listserves, and every once in a while, something comes up that really grabs my attention. Today there was a post by a massage therapist who claims to use essential oils frequently in her practice. She has a house guest whom she states "has been liberally using peppermint essential oil (neat) both orally and topically multiple times per day." Since being in close quarters with her house guest, the massage therapist has experienced severe headaches, flushing, rapid heartbeat and "a severe response similar to popping amyl nitrate".
I've said this often and I'll say it again: essential oils are not toys, they are medicine and must be used with respect. It is irresponsible and just plain stupid to make liberal neat topical and/or oral use of any essential oil. Peppermint (Mentha piperita), in particular, has some very aggressive qualities.
Many people feel that peppermint falls into the "safe" category because it's widely used as a food additive and an ingredient in OTC herbal preparations. It's important to realize that peppermint oil is used in miniscule quantities in these applications, and knocking back a few drops of pure peppermint essential oil repeatedly throughout the day gives the body a vastly higher dose than one would receive from downing a few Altoids. Although peppermint oil has a relatively high LD50, occasionally people have been known to die due to liver failure from overconsumption.
Peppermint oil disturbs the cytochrome P450 liver detoxification system, which means that it can interfere with the metabolism of certain drugs. It is established that the oil is contraindicated with the use of cardiac stabilizing medications, including quinidine. It appears to interfere with calcium channel blockers, and has been anecdotally reported to increase the activity of NSAIDS and naproxen.
Peppermint essential oil contains a significant amount of menthol, ranging from 44-55% of total oil composition. Large amounts of menthol taken orally are hepatotoxic, especially in people with certain hereditary liver enzyme deficiencies. By inhalation, menthol dilates nasal capillaries and can overexcite the CNS, possibly leading to cardiac fibrillation. In Europe, there have been several documented cases of infant mortality from undiluted peppermint oil that was applied around the nostrils of the victims. It is thought that rapid capillary dilation and paralysis of the epiglottis caused nervous and respiratory collapse in these infants. Consequently, use of peppermint essential oil is contraindicated in children under 30 months of age. Overuse of peppermint can also be problematic for heavy smokers of menthol cigarettes.
Late harvest peppermint oils are very high in menthone, which is both neurotoxic and hepatotoxic. Pulegone, comprising 3-4% of most peppermint oils, is also neurotoxic. In laboratory experiments, high levels of peppermint ingested orally produced convulsions and ataxia in rats.
According to the Expanded German Commission E Monographs, oral ingestion of peppermint essential oil is contraindicated for persons with liver damage, gallbladder inflammation and gallstones. The contraindication for gallstones is important to note, because this condition is often asymptomatic. Overweight caucasian women over age 40 are particularly at risk for asymptomatic gallstones.
Regarding the liver disease contraindication, peppermint is a potent liver detoxifier, and someone whose liver function is compromised simply cannot handle that much stimulation to the organ. I witnessed this last year with a client who was using the essential oil via inhalation to control nausea from liver cancer treatment. She did fine with the oil via diffuser, and unbeknownst to me, decided to begin taking it orally under the assumption that it would be even more effective. Two weeks later, her liver enzymes were dangerously elevated and her physicians were in a panic. She came in for an appointment, bottle of peppermint in hand, and I stopped her after she'd taken 3 oral doses in less than 5 minutes. Apparently, she'd been taking about 1.5 ml daily, and neither she nor her doctors ever thought it might cause a problem.
Topically, peppermint essential oil is considered a moderate dermal irritant. In my experience, it has high potential for dermal irritation when used neat on sensitive or thin skinned areas of the body. I recommend mixing it with other appropriate essential oils in a carrier before topical application.
Peppermint is an undervalued oil in aromatherapy, and is effective against an astounding number of pathogenic organisms, including MRSA. It is often underutilized by aromatherapists, however, due to its aggressive character. I don't mean to frighten anyone away from using peppermint oil, but I do want to emphasize that when used inappropriately, as in the case of the affected massage therapist, there is high potential for adverse reaction. Be sensible, avoid oral ingestion and apply topically only when well diluted. When properly used, you'll not only experience the physical and mental benefits of this oil, but you'll be able to enjoy the bright, pungent, head-clearing aroma of peppermint.