Professor Robert Anton (Strasbourg, France) developed the theme of toxicity
and safety, noting that the risks depended both on the variation found in any
particular oil and also on the technology of the preparations used. Chemical
profiling was needed before the toxicity risks of any oil could be assessed.
Relevant concerns were the lipophilicity of the terpenes found in essential
oils, possible synergistic effects, and the different metabolic pathways sometimes
found in humans compared with test animals. An example of the last was the metabolism
of safrole into a carcinogenic compound in animals but into the different, non-carcinogenic
1-hydroxysafrole in humans.
Various biological activities with potential toxic implications had been found
for constituents of essential oils. They included monoamine oxidase inhibition,
phototoxicity, oestrogenicity and genotoxicity.
Some cases of serious reactions, including death, had occurred after ingestion
of undiluted oils, and in France there were special regulations for their pharmaceutical
use to minimise the risks. The Council of Europe had categorised essential oils
into those that were primarily used in nutrition, where small quantities for
intermittent use were not restricted, and those whose use was primarily medicinal,
in which case dossiers were compiled and account taken of long-term use of the
oil without reported adverse effects. In the case of more recently-introduced
oils, a three-month study on two animal species plus tests for genotoxicity,
skin tolerance and allergy would be required.
Professor Anton concluded by emphasising the need for pharmacovigilance. Care
was particularly needed with babies and young children. Since many essential
oils were used in cosmetic products as well as in aromatherapy, and an increase
in allergies was being reported in the European population, pharmacists should
also be aware of this aspect in being alert to any adverse events where essential
oils might be involved.