From naha.org:
Aromatherapy Benefits
Essential oils are powerful tool that may alter, shift, change and adjust mood, emotion and physical issues. It has been historically known to help alleviate stress, skin irritations, depression and anxiety. It also helps our pets achieve over wellness. All 100% pure essential oils are antibacterial. They vary in other properties such as antiviral, antiseptic, anti-inflammatory and so on. Today, we are going to talk about those oils that are all 4 - antibacterial, antifungal, antiviral and anti-infectious.
Quality of Aromatherapy
Why is quality important? Well, it will dictate the level of therapeutic value as well help reduce your exposure to chemical-based products. It is also important when working to enhance overall health and wellness. For example, you may feel relaxed when smelling a synthetic lavender candle but, the combination of synthetic ingredients may bombard and clog the lymphatic system with toxins rather than assist the body in eliminating toxins.
Olfaction Process
Essential Oils have historically been shown to calm and relax emotions as well as enhance focus, attention and memory. To understand this, first it is best to be familiar with the olfaction process. The nose is a protrusion of the brain. Scent enters the body in less than 1 second and travels to the pituitary and hypothalamus to tell your body how to respond to a situation. It will help to relax or stimulate. This message is then sent to the rest of the body via the nervous system. Scent actually dictates how we taste. It is the only sense that does not have to go through the digestive tract or spinal cord to be processes. It immediately goes to the brain and elicits a response. It is also important to note that Richard Axel and Linda Buck (both from the USA) won the 2004 Nobel Prize in Physiology or Medicine for their discoveries of odorant receptors and their relationship to the organization of the olfactory system. http://nobelprize.org/nobel_prizes/medicine/laureates/2004/press.html
Studies
There have been numerous studies done to show that the scent of lavender, when inhaled, affects the beta waves thus reducing stress and promoting calmness. Lavender has been historically used to help Alzheimer patients remain calm, relaxed, stay “here in the moment” longer.