One of the factors that determines the purity
of an oil is its chemical
constituents. These constituents can be
affected by a vast number of
variables, including: the parts of the plant
from which the oil was
produced, soil condition, fertilizer (organic
or chemical), geographical
region, climate, altitude, harvesting
methods, and distillation processes.
For example, common thyme (Thymus vulgaris)
produces several different
chemotypes (biochemically unique variants
within one species), depending on
the conditions of its growth, climate, and
altitude. One chemotype of thyme
will yield an essential oil with high levels
of thymol, depending on the
time of year its distilled. The later it is
distilled in the growing
season, (mid-summer or late fall), the more
thymol the oil will contain.

The key to producing a therapeutic-grade
essential oil is to preserve as
many of the delicate aromatic compounds
within the essential oil as
possible. Fragile aromatic chemicals are
easily destroyed by high
temperature and pressure as well as contact
with chemically reactive metals,
such as copper or aluminum. This is why all
therapeutic grade essential
oils should be distilled in stainless steel
cooking chambers at low pressure
and low temperature.

The plant material should also be free of
pesticides, herbicides and other
agrichemicals. These can react with the
essential oil during distillation
to produce toxic compounds. Because many
pesticides are oil-soluble, that
can also mix into the essential oil.

As we begin to understand the power of
essential oils in the realm of
personal, holistic healthcare, we will
appreciate the necessity for
obtaining the purest essential oils possible.
They may seem costly, but
there can be no substitutes.

Although chemists have successfully recreated
the main constituents and
fragrances of some essential oils in the
laboratory, these synthetic oils
lack therapeutic benefits and may even carry
risks. Why? Because essential
oils contain hundreds of different chemical
compounds, which, in
combination, lend important therapeutic
properties to the oil. Also, many
essential oils contain molecules and isomers
that are impossible to
manufacture in the laboratory.

Anyone venturing into the world of
aromatherapy and essential oils must use
the purest quality oils available. Inferior
quality or adulterated oils
most likely will not produce therapeutic
results and could possibly be
toxic. In Europe, a set of standards has been
established that outlines the
chemical profile and principal constituents
that a quality essential oil
should have. Known as AFNOR and ISO
standards, these guidelines help buyers
differentiate between a therapeutic grade
essential oil and a lower grade
oil with a similar chemical make up and
fragrance.