The status quo, the widely believed “wisdom” of the day, is always difficult to change, however illogical or wrong it may be. Blood letting had been widely used for 1,500 years before physicians figured out that it was not, after all, the ideal go-to therapy for all ills. In that context, 36 years is not a long time, but that’s how long the aromatherapy community has been under the illusion that oils of rosemary, hyssop, sage and thyme should not be used for people with high blood pressure.
In 1964, Dr. Jean Valnet’s book Aromathérapie was published. It was a hugely important publication in the development of aromatherapy, and it had a tremendous impact on my own aromatherapy career. However, the quantity and quality of essential oil research available in the early 1960s was extremely poor. There simply wasn’t very much to go on.
In his book, Valnet lists the above four essential oils as “hypertenseur”, and for each one he gives two references: Caujolle, and Cazal. However, the 1944 Caujolle paper he cites is actually about essential oils of lavender, lavandin and spike lavender, all of which were reported to produce a brief reduction in blood pressure after intravenous injection into dogs. None of the other four oils are mentioned, so clearly, this reference was a mistake.
Caujolle and Franck published two other papers, both in 1945, that Valnet might have in fact be referring to. One was about hyssop oil. Injected iv into dogs, it caused an initial drop in blood pressure and then (since the dose was high enough to induce seizures) blood pressure suddenly increased as the seizures came on, and decreased again when they subsided. This spike in blood pressure was considered to be a consequence of the muscular contractions related to the seizures. Unless used in convulsant doses, hyssop oil is in fact hypotensive. The other paper was about clary sage oil, not sage oil. Injected iv into dogs, it caused a slight increase in blood pressure. This paper also noted that sage oil usually caused blood pressure to reduce. The other reference given by Valnet (Cazal) was a thesis from 1943, which I have not been able to find.
Valnet’s contraindication in Aromathérapie is under “usage interne” – internal use – but he does not give a contraindication for “usage externe”. So, even according to Valnet, massage with any of these four oils would NOT be contraindicated in high blood pressure.
In spite of all of the above, Valnet’s advice has been (a) assumed to apply to all uses of these four oils, and (b) repeated in almost all aromatherapy texts since, at least the ones that give safety advice for hypertension. And other oils have been added to the list over time. However, if you look at the research the surprising conclusion is that there is no evidence that any of the contraindicated essential oils – whether listed by Valnet or anyone else – raises blood pressure. In fact most of them reduce it.
In: Essential Oils and Hypertension – is There a Problem? I explain why I believe that there is no case for contraindicating any essential oil in someone with high blood pressure. As well as closely examining the evidence above, I also refer to more recent research, which confirms that the four “Valnet oils” present no risk. The lack of compelling evidence is reason enough to let go of this chimera. There’s also the fact that aromatherapists have plenty of legal challenges to deal with already, and it makes no sense to add to this burden by coming up with restrictions that are scientifically unsound, and that are based on a mistake made in a book in 1964.