The answer to this is, “Yes.” However that means, yes, so long as they are used as intended. There are some companies who advocate the internal use of essential oils and unless done under the supervision of someone qualified in aromatic medicine this practice is not safe. Neither is, “Raindrop therapy” the dropping of undiluted essential oils directly on the skin. This latter practice is if done regularly at a very high risk of causing sensitisation which can result in very severe skin reactions which in the future can happen even with the use of the oils diluted to the same degree as is normal in aromatherapy massage.
Another practice which is very common is the use of vaporisers or oil burners. With these, they should not be left on for more than half an hour at a time.
All these unsafe practices will not produce problems with everyone who is on the receiving end. If they did, these practices would be outlawed and the sale of essential oils would be under much greater scrutiny.
Lastly and again this does not happen with everyone is photo sensitivity reactions. Most of the citrus oils can cause this as can Basil and a few others. The sap of a number of plants can also cause these reactions, indeed, parsnip and most of the rest of that family of plants will cause a reaction if the sap gets on the skin and exposure to strong sunlight follows. The sap of these plants is a much higher risk than the essential oils mentioned.
What I can say is that the only severe reactions I have read about are from the misuse of essential oils. I have never seen a skin reaction that I have been sure is due to essential oils. (One client had a slight rash after a hand massage but this was in my view more likely to be a reaction to the carrier oil used. (Coconut in this case.) It is interesting to not that my practise of using unrefined oils is more likely to produce an allergy reaction than the use of more refined oils as the latter will not have any proteins present.
To summarise, I would say that used sensibly, my experience both in my practice in Cambridge and in my work with adolescents in Huntingdon Aromatherapy is a very safe therapy. The only fatalities ever recorded with essential oils are from the internal use of them and the only ones of those I have read about are either bottles being left where children can find them or deliberate consumption as a form of self harm.
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