I recently took an online course called Clinical Aromatherapy from the University of Minnesota Center For Spirituality and Healing. Along with some great information regarding the history of essential oils and their evidence-based uses; I took away some even greater information regarding safety in their use and the science behind how they enter the body.
Inhalation is the fastest and safest route of entry into the body for essential oils. When essential oils are diffused, evaporated, steamed, or sprayed; the vapor molecules enter the blood stream through the lungs. Secondly, odor molecules travel deep into the brain through electrical impulses from nerve cells in the nose. The smell part of the brain is overlapped by the emotional part of the brain and interacts with the parts of the brain that connect feelings and thoughts, as well as breathing, heart rate, blood pressure, and memory. This is why the smell of essential oils can trigger physical and emotional feelings such as reduced pain, nausea, fatigue, anxiety and stress.
Most essential oils are safe when administered properly and ill effects from inhalation of essential oils are extremely rare. I recommend avoiding large doses of essential oils, applying essential oils undiluted directly to the skin, and ingesting essential oils of any kind as they can have toxic effects. I highly recommend pregnant women use caution as essential oils can cross the placental barrier and many are contraindicated in pregnancy. Essential oil use for children and pets should also warrant precautions.
By R. Legge Konecny, RN
Halcon, Linda PhD, MPH, RN and Beshara, Mary MSN, RN, CCAP. (2013). Clinical
Aromatherapy. Retrieved from http://www.csh.modules.umn.edu.