In my first two posts on fennel oil, I discussed its many versatile actions. Last week, I highlighted its medicinal use across the continents and discussed the safety of ingesting essential oils. Now, I will conclude my series with some of the factors, along with recommendations, to keep in mind when consuming essential oils, while explaining some specifics about fennel oil.


The Goldilocks Dose- Not Too Many Drops & the “Just Right” Oil


Factor 1: Use the proper dosage

Some of the scare around internal use of essential oils is based on media hype of articles that were reporting on incidences of overdoses. This is a different subject altogether than toxic effects from proper application. Unfortunately, the headlines were misconstrued as “essential oils are unsafe to ingest.” I wrote more details about the facts vs. myths of essential oils safety here and here.


Recommendation: Make sure you follow the instructions on the label of your essential oils so you stay within proper dosage recommendations. As with anything, we need to be especially careful with our little ones. (Please see the children and infants’ section of essential oils on my database.)


Factor 2: Use the right essential oil

With essential oils, quality counts. It’s important to only take by mouth essential oils that are labeled safe for internal use. There are many resources on my database about determining the quality of essential oils.

Adulterated essential oils with synthetic ingredients and fragrances are not safe to swallow, because these fillers are toxic!


Recommendation: Make sure your essential oils are pure and are of the highest standard, especially if you will be consuming them!



Guilt from Dis-Association – Isolated Constituents vs. Essential Oils


Factor 3: Isolated Constituents vs. Essential oils

One of the aspects for safe ingesting of essential oils is knowing the differences that exist between compounds found in pure, quality essential oils vs. synthetic isolates and poorly manufactured products. For example, this international and very LONG guide on the safety of essential oils as flavorings had references that were not considering the synergism of the essential oil or the difference between rodents’ and humans’ metabolism.

Below are two examples of this regarding isolates and fennel oil.


1. Estragole

Not considering the differences between an isolate and the metabolic pathways of rodents vs. humans may be why one of fennel’s constituents, estragole, was initially deemed toxic. However, when further explored for human consumption, it was found to not pose a risk at intended dosages.
According to the EMA (European Medicine’s Agency):

…Exposure to [estragole] resulting from consumption of herbal medicinal products (short time use in adults at recommended posology) does not pose a significant cancer risk. Nevertheless, further studies are needed to define both the nature and implications of the dose- response curve in rats at low levels of exposure to [estragole]. In the meantime exposure of [estragole] to sensitive groups such as young children, pregnant and breastfeeding women should be minimised.” *


*Important note: The studies were using straight estragole and not reporting on the internal use of fennel oil, which was reviewed here. (Another less important note, minimize is spelled differently across seas ;)).


2. Ketones and Seizures

Some have quoted that this essential oil may induce seizures due to its ketone content. When searching for evidence, I found a case report of a woman who ingested a “number of cakes containing an unknown quantity of fennel essential oil.” Once again, this may be an overdose and interaction study versus a “precaution.”


Recommendation: Remember to keep up with general precautions of essential oil usage, but don’t confuse isolates for essential oils and scare tactics for science.



Factor 4: Essential Oils & Side Effects/Benefits- Individuality is Important

Some have concern with fennel’s effect on blood pressure. According to Robert Tisserand, this may be due to a misinterpretation of previous literature using the IV injection of essential oils into dogs. (Why would you inject IV oils into animals!)

I also found an article that fennel “fragrance” could cause a spike in systolic pressure.



Essential oils effect our emotions and stress response through aromatic influence, nervous system feedback, and, if unaware, the presence of synthetic toxins or fragrances in different ways.

Some essential oils are stimulating and you should check this guide and precautions on the label, especially if you have a medical condition. However, all bodies react differently to essential oils, for some “stimulating” oils may be relaxing. This could be based on the fact that an oil is more than the sum of its parts. Therefore, make sure you also consider your personal biochemistry and keep in mind the influence essential oils have on our response patterns and that they are holistic.



Factor 5: The Debate Among Experts

Some may be hesitant to use essential oils internally due to the different schools of aromatherapy expressing alternate viewpoints on the safety of their ingestion.

This article provided an overview of the internal use of essential oils from a more conservative viewpoint. The author expressed how even if some aromatherapists don’t feel essential oils should be taken by mouth, they are absorbed into the body by multiple applications regardless. Furthermore, many of these same practitioners are using essential oils internally via suppositories, mouthwashes, and on or in other orifices (i.e., nose, ears).


Recommendation: Find a practitioner or expert you trust and that has experience, especially if you are new. Make sure you research their background, schooling, and clinical expertise. Don’t confuse scare tactics for science.




The issue of safety and proper dosage is very important point to consider with anything you put on or in your body. In general, if you use the oil as intended, check interactions with medications, be mindful of cautions, and don’t overdose, you should be good to enjoy those bitter greens with a little bit of sweetness!



New on the Healing, Health, & Wellness Blog

“Good” Food, “Bad” Food, the “Forbidden Food”: Chewing on the Problem of Moralizing Food Choices

Read more here.



Expanded German E Commission (ABC). Fennel Oil:

The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. 1998.

European Medicines Agency. Evaluation of Medicines for Human Use. Fennel Oil.

FDA. Code of Federal Regulations Title 21. Part 182- Substances Generally Recognized as Safe (GRAS).

The Internal Use of Essential Oils: An exploration (School for Aromatic Studies):

A Procedure for the Safety and Evaluation of Flavouring Substances.


This review describes a procedure for the safety evaluation of flavouring substances. Over 2500 flavouring substances are currently in use in food. While toxicity data do not exist on all flavouring substances currently in use, within structurally related groups of flavouring substances many do have toxicity data and this information along with knowledge of structure-activity relationships and data on the daily intake provides a framework for safety evaluation. The safety evaluation procedure provides a scientifically based practical method of integrating data on intake, structure-activity relationships, metabolism and toxicity to evaluate flavouring substances in a timely manner. The procedure has been used recently by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) to evaluate a total of 263 flavouring substances.

Joint FAO/WHO Expert Committee on Food Additives. Food Chem Toxicol. 1999 Feb-Mar;37(2-3):207-32. Available at:

Plant essential oils and allied volatile fractions as multifunctional additives in meat and fish-based food products: a review. Food Addit Contam Part A Chem Anal Control Expo Risk Assess.

Foeniculum vulgare: A comprehensive review of its traditional use, phytochemistry, pharmacology, and safety. Arabian Journal of Chemistry. November 2016.

Fennel. Natural Standard Database.,-herbs-supplements/professional.aspx?productid=311

Fennel Oil. Examine.

Gori L, Gallo E, Mascherini V, Mugelli A, Vannacci A, Firenzuoli F. Can Estragole in Fennel Seed Decoctions Really Be Considered a Danger for Human Health? A Fennel Safety Update. Evidence-based Complementary and Alternative Medicine?: eCAM. 2012;2012:860542. doi:10.1155/2012/860542.

Epileptic seizure induced by fennel essential oil. Epileptic Disord. September 2011.

Effects of fragrance inhalation on sympathetic activity in normal adults. Jpn J Pharmacol. 2002.



Disclaimer: This information is applicable ONLY for therapeutic quality essential oils. This information DOES NOT apply to essential oils that have not been tested for purity and standardized constituents. There is no quality control in the United States, and oils labeled as “100% pure” need only to contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. The studies are not based solely on a specific brand of an essential oil, unless stated. Please read the full study for more information.

This material is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. You should check with your doctor regarding implementing any new strategies into your wellness regime. These statements have not been evaluated by the FDA. (Affiliation link.)

Thanks for the pictures Pixabay!