“Because the limbic system is directly connected to those parts of the brain that control heart rate, blood pressure, breathing, memory, stress levels, and hormone balance, essential oils can have profound physiological and psychological effects… Olfactory responses to odors induce the brain to stimulate the release of hormones and neurochemicals that in turn alter the body’s physiology and behavior.”
Essential Oils: Desk Reference. 4th ed. Orem, UT: Essential Science Pub., 2007. Print.
Please also keep in mind that essentials oils are very powerful as they directly affect the Limbic System and can bring up some painful and traumatic experiences.