Essential oils are highly concentrated plant extracts – the “essence” of the plant – that have powerful healing properties. Massage therapists and aromotherapists use them – even some cooks use them! But what most us probably don’t know is that only about 2% of essential oils sold in the United States is true therapeutic grade, as determined by the International Standards Organization (ISO).

As demand for essential oils grows – and store shelves get more crowded – therapeutic grade oils are getting harder to find. It also gets tougher to distinguish therapeutic grade oils from inferior grade oils, which are used mainly as fragrances. True essential oils stimulate the immune system and have a wide range of antimicrobial and/or antinflammatory properties.

So what makes a therapeutic-grade essential oil?

Essential oils come from different parts of plants, including seeds, bark, leaves, stems, roots, flowers and fruit. An entire plant might produce only a drop or two of oil, making oil vastly more potent than dried herbs. These are highly complex, highly volatile substances, with as many as 400 different chemical constituents. Different batches of the same oil can have different therapeutic properties, depending on the variations in their chemical makeup.

Most pure oils are slowly steam-distilled from the plants in stainless steel, nonreactive cooking chambers, using the lowest possible pressure and temperature.  (Certain types of oil, such as citrus, are expressed from the fruit rind. While technically not “essential,” these oils are still beneficial if expressed from organically grown fruit. Other types, such as neroli or jasmine, can only be extracted using solvents, and cannot be taken internally.)

High temperatures and/or pressure, or contact with reactive metals such as copper or aluminum can quickly destroy the delicate aromatic compounds in the oils. And that’s the key to producing therapeutic-grade essential oils...to preserve as many of these compounds in as high a concentration as possible. 

The purity of an essential oil is also determined by its chemical constituents, which are affected by a wide range of variables. These include the climate, soil conditions, and altitude in which the plants grew; the type of fertilizer and harvesting method used; and the parts of the plant used in for distillation. Even the growing season can affect the concentration of the different compounds. For example, the key compound in thyme, thymol, is present in a much higher concentration in oil distilled at the end of the growing season, in the late summer or fall.

Most of the essential oils you see on store shelves or in online catalogs are not true therapeutic grade. They may have additives such as water, alcohol or other chemical solvents, or they may contain pesticide or chemical residues. Oils marketed as “essential” can also in fact be diluted and/or adulterated with synthetic fragrances or solvents. They may be the products of the second or third distillation of the same batch of plants and therefore much less potent.

The only sure way to judge whether an essential oil is therapeutic grade is through gas chromatography (GC) purity testing, a highly sensitive procedure that measures whether the various components of an essential oil are present in precise percentages. If the percentages are off, then it’s not therapeutic grade. In this way trained GC testers can examine the entire chemical profile of an oil to determine if the oil is pure or adulterated. That said, even GC isn’t foolproof, because in the case of some types of essential oil, the testing can’t distinguish between synthetic and natural versions of the same compound.

Essential Oils in Skin Care
For your skin to reap the full benefit of therapeutic-grade essential oil, you need only a few drops blended with pure vegetable-based carrier oil. Examples of the latter include coconut oil, apricot kernel oil, and rosehip oil. Because essential oils are fat-soluble, they blend well with the carrier oil – and they are highly compatible with your skin’s chemistry.

The carrier oil provides the emollient qualities that we look for in a skin cream. The essential oil provides the healing properties. Some, such as lavender, are powerfully anti-septic and anti-inflammatory and can help reduce scarring. Others, such as frankincense, can help prevent the breakdown of skin cell membranes from environmental toxins.

Fragrance For Life
Essential oils also provide the fragrance factor – that indefinable quality that occurs when the oil’s vapor molecules are released. Scientists are only just beginning to explore and understand how aroma reaches and influences the human body and emotions.

As we inhale these molecules, they trigger electrical impulses to the limbic lobe, the brain’s emotional control center. Emotions such as joy, anxiety, depression, fear and anger all emanate from this region of the brain, which also controls memory, stress levels, blood pressure and hormonal balance. The stimulation provided by essential oil aromas thus can have profound effect on both the body and the mind.