I found this link this morning while browsing. I looked at it because it was an NHS web address though in fact the PDF belongs to a cancer charity. It is short on detail and there is little I could find to disagree with except that it seems to have been cribbed from a US website. While it quotes typical prices of treatments in English pounds, when it talks about regulation it says, “therapists do not have to be registered to practice. Therapists may choose to register with one of the two federal regulatory bodies that have recently been set up.”
There are hundreds if not thousands of papers written about individual essential oils and there use in treating different conditions. Far too many for me to have looked at more than a handful of them. This report suggests that while aromatherapy oils used via a diffuser might lower blood pressure if used for up to one hour, used for two hours blood pressure actually rises above the base level. The report suggests this may actually be dangerous for spa workers.
Anxiety is an area where there are lots of studies, some based on a self rating scale, and others measuring things such as cortisol levels. (This can be done via saliva so there is not the problem of needles causing the anxiety to rise again!) This is one of the many links I found when putting “Aromatherapy research anxiety” into Google. As with most of the articles I have found the conclusions almost inevitably state something like, “Aromatherapy may help reduce anxiety.” This highlights the fact that research on aromatherapy oils is despite their use over centuries in some cases, very much in it’s infancy and as there is not the financial might of large pharmaceutical companies behind it this is unlikely to change quickly. Even if all practitioners were to complete some case studies every year it would still be difficult to get evidence of the quality provided by double blind trials.