An essential oil is a water-immiscible material produced by distillation from some plant material. The material (flowers, leaves, stems, or roots, depending on the plant) is put in an alembic over water, and the volatile compounds, which require less vapor pressure to evaporate with the presence of steam, distill into a receiving vessel. The upper portion is the oil, the lower being the hydrosol. They are drained with two spigots. Most oils are distilled in a single process. The exception is ylang-ylang, which takes 22 hours to complete distillation. It is distilled fractionally, producing several grades.
Many vendors will sell fragrance oils which are not pure and often lack the effect of true essential oil. It is only recommended to use essential oils that have been stored in amber or dark glass, and are labeled therapeutic-grade. Some of the oils are hot, like Oregano. Therefore, caution should be used when putting them on the skin undiluted. If needed, essentials oil can be diluted with a carrier oil like grapeseed oil or sweet almond oil.
Many essential oils have medicinal properties that have been applied in folk medicine since ancient times and are still widely used today. For example:
Aromatherapy is a form of alternative medicine, in which healing effects are ascribed to particular fragrances. To read the experiences of those using essential oils for natural healing, visit the Essential Oil Testimonials (http://www.oil-testimonials.com) website.
Prior to the discovery of distillation essential oils were extracted by pressing, and this is still the case in cultures such as Egypt. Traditional Egyption practice involves pressing the flower and then burying it in unglazed ceramic vessels in the desert for a period of months to drive out water. The Lotus oil retaining it's scent after 3000 years in alabaster vessels in Tutankhamun's tomb was pressed, rather than distilled.