In the eighteenth century, John Hill wrote in the Family Herbal: “Sage will retard the rapid progress of decay that treads upon our heels so fast in latter years of life, will preserve faculty and memory more valuable to the rational mind than life itself.”

Hill's comment reveals two somewhat remarkable facts: though Alzheimer's disease wasn't “discovered” until the early twentieth century, knowledge of dementia has existed for a very long time and secondly through centuries of observations Europeans (and others) knew that aromatic plants were useful in treating dementia.

Now scientific knowledge and historical observations have begun to merge, as we come to understand the chemical processes by which the essential oils used in aromatherapy help combat dementia. Specifically, essential oils prevent and partially reverse the damage done to memory by oxidants, most notably by peroxynitrites.

Peroxynitrites are the chief cause of memory impairment in Alzheimer's disease, as they prevent the formation of acetycholine, the main compound involved in memory retrieval. The chemicals in essential oils convert peroxynitrites into nitrogen dioxide and water. They also add hydrogen back to choline transport systems, muscarinic receptors (involved in the uptake of choline), and choline acetytransferases (the enzyme that puts acetylcholine together), thus increasing the production of acetylcholine and thereby partially reversing memory deficits.

Case studies of improvement in language skills, awareness, alertness, and short-term memory in Alzheimer's patients using aromatherapy are now being bolstered by a series of small-scale clinical trials. To quote from one of these trials: “In conclusion, we found aromatherapy an efficacious non-pharmacological therapy for dementia. Aromatherapy may have some potential for improving cognitive function, especially in AD patients” (Effect of aromatherapy on patients with Alzheimer's disease). In this trial, the essential oils used were rosemary, lavender, orange, and lemon.

A review of clinical trials involving sage and lemon balm similarly concluded: “These herbal treatments may well provide effective and well-tolerated treatments for dementia, either alone, in combination, or as an adjunct to conventional treatments” (The psychopharmacology of European herbs with cognition- enhancing properties).

Historical observations, case studies, and clinical trials indicate that the chemicals contained in essential oils are surprisingly effective in the treatment of Alzheimer's disease. Perhaps, modern medicine despite its emphasis on expensive synthetic drugs with harmful side effects will one day come to the same conclusion that John Hill did more than two hundred years ago.