By Marco Valussi
The oral intake, in its various forms, and along with inhalation, allows the fastest and most massive absorption of essential oil. The difference is that in inhalation the total amount of oil offered to absorption is almost never very high because it is difficult to inhale very high doses of essential oils. In ingestion, however, it is possible, especially by using capsules, to take high doses of essential oil. This fact, alone, explains why oral administration is one of the most delicate modalities from the point of view of safety. Of course, as almost always in life, the dose is significant. Every day most people consume essential oils by mouth, eating raw vegetables, drinking an aromatic herbal tea, brushing teeth with a toothpaste, chewing chewing gum or a balsamic candy. We also assume very toxic essential oils, such as absinthe, by drinking certain liqueurs. It is thus clear that at least some essential oils are not so dangerous that we cannot use them by mouth. But the amount of essential oils we introduce in this way is very low compared to those used in therapy. In the first case, it is in terms of parts per million (ppm), while in the second case percent dilutions are used (%).
Let's give an example: an absinth liquor has approximately a concentration of 60 ppm (or 0.006%) of wormwood essential oil; by drinking 20 ml of absinth liqueur we are taking 0.0036 ml of essential oil, or a tenth of a drop. If I take a capsule containing 5 drops of essential oil (a not particularly high dose) I'm taking a 50 times higher dose of essential oil! Indeed, the same legislation recognizes this difference. Essential oils that are certified as safe for intake as food aromas are not deemed safe for higher dosing.
Oral use for therapeutic purposes is a completely different matter. Since significant doses of the substance are taken, there must be a reasonable certainty that the oil is safe at the dose used, the proper dilutions and galenical forms should be used. Essential oils are different from one another, and some may contain toxic molecules even at low doses, and most contain molecules that can cause problems if used at excessive doses. That is why subjects in special conditions such as children, pregnant women, elderly, allergic subjects should pay particular attention to the oral use of essential oils. Furthermore, the idea that essential oils, as derived from a natural source, cannot cause adverse effects, is completely unfounded. Not only because there is nothing inherently secure in plant derivatives (some are safe, others no, the evaluation has to be individual), but also because essential oils are among the most active plant extracts, and therefore potentially even more toxic. We must not forget that taking important doses of essential oils puts a burden on the liver and on other sites of detoxification in our body. Essential oils for our system are a xenobiotic, an external substance that could be dangerous. Our body then uses metabolic steps (in the liver, intestine, lungs and skin) that should reduce its toxicity and make it more water-soluble and eliminate it with urine. But it can happen that these substances are little or badly metabolized, concentrating in the liver and leading to toxicity (in the case of 1,8-cineole) or that they metabolize but that metabolites are more toxic than essential oils and that they can express their toxicity on the liver (as the primary site of detoxification), or even detoxification complicates our system, making us less efficient in detoxifying other substances (perhaps reducing our liver glutathione stocks).
There is also the very important issue of the administration and type of vehicle used. For example, it is possible to use peppermint oil by mouth, and in fact, peppermint essential oil-based products with or without essential oil of Carum carvi have existed for years. These products are formulated into gastro-resistant capsules, but taking the same amount of essential oil by mouth in an unprotected manner would certainly lead to adverse effects and irritation.
Conclusion: any drug-related therapeutic action, including the ingestion of significant amounts of essential oils, includes the possibility of side effects, interactions and toxicity. This does not mean that you cannot use them, indeed, but to do this you need to know which oils are effective, which ones are safe, what dosages and in what galenic form it is best to use them, and if the whole thing is worthwhile. Consult a professional and be wary of those who suggest oral essential oils as a risk-free panacea.