Aromatherapy is one of the most popular complementary therapies. Natural products have proven and very interesting impacts on the body and mind which is attracting increasing research attention. Researchers sense there are Nobel prizes to be won in this area.
Safetywise the essential oils used in aromatherapy have a lot going for them simply because steam distillation, the method by which essential oils are separated from plant matter, limits the size of molecules which form an essential oil. Some are very tiny indeed. The smaller the molecule the safer the natural product and the easier it can be eliminated from the body.
Certain plant families like the lamiaceae produce essential oils which contain a wide range of molecules used by the plant to defend itself from predators and attract pollinators and which are very safe indeed.
All information on essential oils positive and negative, true and false is of value. The lack of negative information doesnt in itself confirm the safety of essential oils but it is suggestive.
As we venture away from the safe 60 oils we must take extra care particularly if members of the public rather than trained aromatherapists are buying the oils. For example Parsley oil sounds harmless enough. However it contains apiol (18%) which is toxic (http://en.wikipedia.org/wiki/Apiol).