How many lemons are in a 15 ml bottle of lemon essential oil? Do essential oils expire? How do you test the purity of essential oils? The answers to these questions are just a few of the things I’ve learned, nearing the end of Module 2 of Foundations of Aromatherapy, one of two courses needed for aromatherapy certification through The School for Aromatic Studies.

Disclosures and Disclaimers

The Cold Pressed Truth

True essential oils are distilled or cold pressed. While citrus oils can be distilled, they are usually cold pressed. Citrus essential oil is found in pockets within the peel of the fruit. Initially, citrus essential oils were expressed by hand, literally squeezed out of the peels. Today, citrus essential oils are cold pressed. The fruit runs through machinery that contains hundreds of tiny needles that puncture the peel, releasing the essential oil. So what about references, like it takes 1/4 of a lemon to make 1 drop of essential oil, or it takes 75 lemons to make a 15 ml bottle of lemon essential oil? It might be more accurate to say 1/4 of a lemon peel or 75 lemon peels. The fruit of the lemon is different than the essential oil that resides in its peel.


Essential oils have a shelf life of 2-5 years, depending on what type of essential oil and how it’s stored. Citrus oils tend to have a shorter shelf life, 6-12 months, than other essential oils. I can’t imagine not using an essential oil within 6 months to 5 years, but I’m keeping these time frames in mind. Essential oils, with use and over time, combine with oxygen and oxidize. Using an oxidized essential oil could cause an adverse reaction. Here are a few things you can do to slow the oxidation of an essential oil:

  • Store essential oils in amber or blue bottles in a cool, dark place.
  • Bottles with orifice reducers are the best barriers to oxygen.
  • As you use an essential oil that is in a larger bottle, move the oil to a smaller bottle to keep the space between the oil and the top of the bottle at a minimum.

Purity Testing

There are a number of ways essential oils can be adulterated. Alcohol, vegetable oil, a synthetic chemical or a less expensive essential oil may be added to an essential oil to stretch the amount of the essential oil. A synthetic product or less expensive essential oil may be substituted entirely for the essential oil. A common example is the substitution of lavendin for lavender. You may experience an adverse reaction to an adulterated essential oil, as you would with an oxidized essential oil, because the components of the essential oil have been altered.

An overall approach to determining the quality and purity  of an essential oil includes doing as much research as you can as to the origin of the plant material, manner of processing and chemical analyses. In addition, there are some simple tests you can do at home:

  • Evaporation – Put a drop of the essential oil on a piece of blotting or watercolor paper. In 24-48 hours, most pure essential oils will evaporate completely, unless the essential oil has a color to it, such as citrus oils.
  • Water – Put a drop of essential oil in a glass of water. If the water becomes discolored or cloudy, the essential oil likely has water in it, in addition to a substance to keep the oil and water together. Because oil and water don’t mix.
  • Carrier oil –  Rub a drop of essential oil between two fingers of one hand and a carrier oil, such as grape seed oil or olive oil, between two fingers of your other hand. Pure essential oils are not greasy.
  • Smell test – The nose knows, but it may take some practice. Pure essential oils do not smell like chemicals or perfume, but rather like the plant material from which they were processed. You may have acquired a good sense of smell through the usage of essential oils, or you can practice with different brands of the same essential oil or the plant material itself, like lavender or peppermint herbs.

Until next time, you must be sure that your oil is pure.

Oils & Spoils Certifiable Facebook Group

I’ll continue to share highlights of what I learn on my journey to aromatherapy certification. For those of you who would like to join me on this journey, I’ve created the Oils & Spoils Certifiable Facebook Group, a support group dedicated to helping its members attain their aromatherapy certification(s) and pursue other essential oil educational opportunities through The School for Aromatic Studies. To join the group, contact me to let me know the course in which you’re enrolled.

Certification courses:

Foundations of Aromatherapy – An excellent primer for essential oil users, whether just beginning or experienced. Completion of this course is required before beginning Aromatic Scholars: Aromatherapy Certification Program and highly recommended before taking the French Aromatherapy course.

Aromatic Scholars – Aromatherapy Certification Program – Following completion of Foundations of Aromatherapy, complete this course to become a Certified Clinical Aromatherapist.  Payment for the course can be made over three months.

Foundations and Aromatic Scholars Program – the two courses above, combined for a savings of $200.

French Aromatherapy Certification Course – Earn a certificate in French aromatherapy, which offers more in-depth information on safe, internal usage of essential oils.

Balms, Butter and Salves Certification Program – Learn how to make Lip balms, Body balms, Salves, Body butter, Natural Deodorant, Massage butter, and much more. Sign me up after I complete my other certification classes!

Aside from certification courses, The School for Aromatic Studies also offers courses on blending, botanical body products, aromatic applications for the skin, and more.