The history of aromatherapy goes back some six thousand years to the ancient civilisations of the Mediterranean, such as Greece, Italy and Egypt. Initial uses of aromatherapy were more for perfuming than for healing or cleansing. It was used to perfume away body odor and other unpleasant things that people were not too keen on smelling.
A lot of the plants from which essential oils are derived are plants which only thrive in such warm weather climates as the Mediterranean countries. Aromatherapy oils were either applied directly to the body to disguise unpleasant odors or they were added as diffusions to baths or massaging oils.
Essential oil uses began to become slightly medical when it was discovered that some oils had cleansing and anti bacterial properties. The use of essential oils started to become more a question of health maintenance rather than bettering the air surrounding oneself. Over time and mainly through anecdotal evidence, the healing properties of different essential oils were slowly being discovered.
Fast forward to France in the 1930's and aromatherapy as we know it today was born. This time was also the birth of the term aromatherapy, meaning the use scents to heal the mind and body. A curious fact about the man who coined the term aromatherapy, is that he did so out of amazement that lavender oil cured burns on his body without leaving scars behind. This is interesting because applying essential oils directly to the body is not the most common form or typical use of aromatherapy. Indeed many practitioners advise against it almost as strongly as they advise against ingesting essential oils.
Today, the term most often applies to using the actual scent to bring about change, such as a diffuser spray changing the atmosphere in a room or in your entire house. Massaging with essential oils diluted in carrier oils is considered mainstream aromatherapy, but simply applying essential oils to one’s skin is not considered good practice and can, in some circumstances, cause more harm than good.
Starting in the 1930s, people began to experiment to find out all of the various things that essential oils could either cure or mask the symptoms of. As mentioned above, such experimenting was done in an ad-hoc way, most often in the form of someone reporting their own usage and results of a particular oil.
Essential oils are not tested or recommended by the likes of the FDA and they are still mostly all natural. However, being all natural does not mean that it is completely safe and it certainly does not make any sort of claim about whether or not the product will work at all for what you are using it for.
It also does not tell you what the known or possible side effects of use are. The history of aromatherapy has come a long way in 6000 years, but nowhere near as far as it needs to go in order to take its proper place among the modern medicines of the western world.