The term “oil” in herbal medicine can be a confusing matter without clarifying exactly what type of “oil” we are talking about. The generic term oil can refer to two distinct herbal preparations. In one type, herbs are extracted with a fixed oil, usually vegetable oil, to make infused herbal oil intended primarily for use on the skin. The other products, essential oils, are phytochemical constituent groups isolated from aromatic herbs. An important point here is that essential oils are both plant constituents and when isolated from the plant, herbal products.
Culinary oils like Olive oil used in making infused herbal oil are lipids or fats. Lipid-based oils are also known as fixed oils because they are non-volatile. Fixed oils consist in part of fatty acid chains and are best known in the realm of nutrition. The highest quality fixed vegetable oils are cold-pressed from the fatty fruits and seeds whose names they bear. Olive and sesame oils are the most commonly used oils in herbal dietary supplements today, but many others can be found in herbal cosmetic products.
To make infused herbal oils like Calendula and St. John’s Wort, Herb Pharm uses a traditional process called digestion. Digestion is a very low heat, prolonged extraction designed to draw out the plant’s bioactive compounds. Herb Pharm uses food-grade, cold-pressed, certified organic extra virgin Olive oil to make our infused oils. Fixed oils dissolve many of the same compounds that dissolve in pure alcohol and the resulting infused oil represents a whole herb extract of the plant.
Fixed oils are distinct from the very fragrant essential oils. Essential oils are highly aromatic, volatile plant oils that are commonly used as fragrances, flavorings and in aromatherapy. These oils tend to evaporate or volatilize fairly easily at moderate temperatures. It is this volatile character that allows their aroma to reach your olfactory receptors and be perceived as fragrant. Natural essential oils occur in complex combinations that have a fairly specific composition for each plant. In herbs like Peppermint, Lavender and Cinnamon, the unique phytochemical composition of each essential oil is responsible for the highly distinctive aroma of the plant.
Essential oils can be separated from plant material by extracting them with certain types of solvents and in many cases by passing steam through the herb. Some essential oils are collected by simply pressing the fresh plant, as in the case of Orange oil used to flavor Children’s Echinacea™. Steam distillation is widely used to produce essential oils and is the method used for our Tea Tree oil and other essential oils we use as ingredients. We eschew chemical solvents and never use essential oils that are extracted with them.
The chemistry is complex, but it is the hydrophobic or water-repelling nature of essential oils that allows for their isolation and collection through steam distillation. And since both essential oils and fixed oils are hydrophobic, they are very compatible with each other. Fixed oils are commonly used as carriers and diluents for very strong essential oils. This combination is commonly seen in products like massage oil.
In line with the “like dissolves like” principle, essential oils are also highly soluble in strong alcohol. This forms the basis for the old pharmaceutical preparations known as “spirits.” Herb Pharm makes several spirits as combinations of a liquid extract or tincture with the essential oil of the plant rather than a simple alcohol solution of the essential oil. Our spirits include Oregano Spirits™ and the very popular Peppermint Spirits. One similar product is Erigeron/Cinnamon Compound that combines essential oils of these two plants in high alcohol. Another related product is Friar’s Balsam that contains several balsams, which are chemically closely related to essential oils, dissolved in alcohol.
Tea Tree Oil represents the only essential oil product that Herb Pharm carries. In all other cases the essential oils we use are ingredients in other products, but our Tea Tree is a pure, standalone essential oil. Essential oils represent large quantities of plant material and are therefore very powerful plant derivatives that should be used sparingly and carefully.
In contrast, the infused oils like those made from Calendula, Arnica and St. John’s Wort are very soothing to skin because of their fixed oil bases. Each of these herbs brings their vulnerary or skin healing properties to their respective infused oils. These single oils are also combined in our aptly named Trauma Oil™. Two other special oil-based formulas are our Mullein/Garlic eardrops and Herb Pharm’s Original Salve™. While tinctures or liquid extracts comprise the bulk of our product line, these two distinct categories of oils are important contributions to the Herb Pharm medicine chest. Our infused oils constitute a very visible and significant part of our external product profile. Herb Pharm’s essential oils may not be as apparent, but they establish a noteworthy category of flavoring and active ingredients throughout our products.
Originally Published in June 2010