Sometimes when I write I seem to be in 8th grade again, trying hard for an A from a difficult teacher (won't my dad be proud?). It doesn't feel like the real me but since I already wrote this, maybe some of you will be interested.
Aromatherapy is a fusion of old Eastern wisdom and contemporary science. Essential oils, the basis of aromatherapy, are the most complex (chemically speaking) and concentrated plant essences in the world. Almost all essential oils are used to make perfume and cologne and the rest is used (hopefully) in it's pure form. What is known empirically about the effect of essential oils on our emotions and brain is limited. What we do know is that our sense of smell is immediately processed in the limbic system of the brain- our seat of emotions. It is pretty safe to say that it's a good idea to surround yourself with good, pleasant smells for limbic health.
Frequency is the measurable rate of electrical energy flow that is constant between any two points. A healthy human body has a frequency of between 62&72MHz. Processed/canned food has a frequency of zero. Fresh produce has up to 15 MHz, dry herbs from 12 to 22 MHz and fresh herbs from 20 to 27 MHz. Essential oils start at 52 MHz and go as high as 320 MHz, which is the frequency of rose oil. Essential oils have the highest frequency of any natural substance.
Unfortunately, a higher volume of essential oils are sold than are grown. Any oil sold by a street vendor is almost certainly mixed with proplyene glycol (a known carcinogen), and the oils sold in grocery stores aren't much better. If you are looking at something that would ordinarily be safe to consume like basil or peppermint and it says "don't use internally", that is a sign that it has been mixed with propelyne glycol. I have noticed almond oil marketed as a massage oil base that has the "do not consume" tag, when you could walk down the isle and buy organic almond oil for cooking (or massaging) cheaper!
So the idea is to get your hands on "therapeutic grade" essential oils. What that generally means is that the oil was distilled using low pressure and/or heat, and is free of pesticides and additives. Excessive heat disturbs and mutates the complex chemical structures of the oils- that is why aromatherapy candles are useless (besides smelling good). While therapeutic grade oils have many tested uses and actions on the physical body, again the research isn't there to make a definative statement about their effect on mood.
Some oils I've used with success. Frankincense, reported as having antideppressant properties, has a very rich, uplifting smell that also aids in meditation. There is also anecdotal evidence that it fights cancer- when I quit smoking I will be using it a lot as a preventative measure. The blend Trauma Life was created for Steven Segal to use with hospital patients he has worked with. It is calming, relaxing, yet also stimulating. One of it's ingrediants is essential oil of Valerian root which has been demonstrated to be a central nervous system sedative. When I was having panic attacks I tried to always keep this oil with me. There is even a blend called SARA- shorthand for sexual and ritual abuse, touted as helping release negative emotions that are locked in the body.
It's good to take these claims with a grain of salt. On the physical side, oils are oxygenating and can help deliver nutrients to the cells. They raise your frequency. There are also oils and supplements that detoxify the liver, helping tremendously with overcoming "blueprints of addiction" in the liver. Studies done in Japan with diffusing the oil Lemon in office buildings found productivity was raised 50%. Almost all oils are highly antimicrobial; soaps using an oil as a base are a good alternative to mass-market antimicrobial soaps that use triclosan (which is chemically related to agent orange, besides _that_ there is concern that bacteria et all readily mutate to get around simple, uniform chemicals. Enter the complexity of essential oils and that no two oils from different harvests will be the same.)
Uses: the safest way to use them is to smell them from the bottle or diffuse them without heat (excessive heat disrupts the oils- aromatherapy candles would not be considered of therapeutic quality). To apply them to the skin first dilute in olive oil or another massage oil base and then test your reaction to the oil on the bottom of your feet. You can also ingest certain oils, but only after you have done research and have a very high quality consumable oil.
They are a tool to find balance emotionally and an exciting field of research in their actions on the physical body.