For the Love of Science…

Can We Stop the Chit-Chat on Lavender, Tea Tree, and Man Boobs?!


Listen to “A Brief Review of the Latest Study Regarding Tea Tree and Lavender Oils’ ‘Endocrine Disruption‘” in 5 minutes below.


Listen to this blog in less than 12-minutes below:


Recently, the media got wind of a study that set essential oil lovers in a state of hormonal confusion… again. This “concern” is not new.

The scare was based on the reporting’s of an experiment that used isolated constituents found in tea tree and lavender oil. The conclusions were extrapolated from findings found in human cancer cells in a petri dish. The researchers reported that essential oils, which were not tested in their intact form, were potential endocrine disruptors. This was due to the effects of these constituents’ actions on hormonal receptors and gene transcription activity in the cells.

I provide a basic overview and summary of the issues here. I discussed:

  1. How compounds in essential oils can have differing effects in petri dishes, living beings, and humans.
  2. That petri dish studies have not been conclusive.
  3. How a previous scare stating that young boys would grow man boobs with certain essential oils was flawed. The cases that were highlighted were really related to consumer products that contained tea tree and lavender, not the therapeutic, grade essential oils themselves.

Now, it’s time to dive a bit deeper, for those who wish to jump in with me.

Come on in, the water’s fine!



More Details on the Study: Isolation of Constituents in Petri Dishes

For those who want more details on the actual constituents studied and the methods of the experiment, here it is:

Under Korach’s direction, Ramsey and his NIEHS colleagues went a step further. From the hundreds of chemicals that comprise lavender and tea tree oil, they selected for analysis eight components that are common and mandated for inclusion in the oils. Four of the tested chemicals appear in both oils: eucalyptol, 4-terpineol, dipentene/limonene and alpha-terpineol. The others were in either oil: linalyl acetate, linalool, alpha-terpinene and gamma-terpinene. Using in vitro, or test tube, experiments, the researchers applied these chemicals to human cancer cells to measure changes of estrogen receptor- and androgen receptor-target genes and transcriptional activity.

All eight chemicals demonstrated varying estrogenic and/or anti-androgenic properties, with some showing high or little to no activity, the investigators reported. Ramsey said these changes were consistent with endogenous, or bodily, hormonal conditions that stimulate gynecomastia in prepubescent boys. (source)

In plain English, the researchers took eight constituents, out of hundreds, concentrated them, and placed them in a dish with human cancer cells. The conclusion was that because human cancer cells had changes in their gene activities of estrogen and androgen receptors, that the synergistic, therapeutic essential oil would behave that way in the male body and cause them to get women boobs.

Research that isolates one compound from a natural source and generalizes it to the whole plant or substance in its whole form is rampant and misleading in the supplement and natural health world. I discussed the pitfalls of this with vitamins here.

Similarly to how isolating and mega-dosing a vitamin and/or mineral without considering its interacting and complementary components can create more imbalances or even harm to individuals, ignoring the synergism of essential oils and disregarding the complexity and intricies of their natural design is also short-sighted. As I discussed in this article published on the Natural Path website:

As you can see, there is complexity to essential oils. Essential oils contain a wide array of constituents, regardless of how they are classified. These all have synergistic or differing therapeutic actions and mechanisms, which can support and balance out one’s biochemistry. Furthermore, one constituent can have multiple actions. For example, alcohols can be antimicrobial, antiseptic, tonifying, balancing, spasmolytic, anesthetic, and anti-inflammatory.5

Their chemical composition can also vary depending on the season of harvest and methods of extraction (distillation, hydrodistillation, super critical carbon dioxide extraction, and solvent extraction- the latter two are not technically essential oils). A final intricacy of an essential oil’s action to consider is its chemotype or distinct plant population within the same species. These various populations produce differing plant secondary metabolites that have differing effects.5,6,8,

There is also a difference in effects and processing between synthetic isolates formed in labs and those found in nature, as pure essential oils constituents. I discussed this in this post, and gave the example of wintergreen:

Regarding the oil of wintergreen and toxicity, most toxic reports are based on its constituent, methyl salicylate. I have a chemist friend who explained to me the difference between synthetic methyl salicylate and that found in wintergreen oil. He said methyl salicylate manufactured in labs is from salicylic acid. Chemists will add sulfuric acid and methanol, both toxic compounds, to produce the methyl salicylate. This is a very different process than distilling wintergreen oil. The video below explains more…


The Estrogenic Environment: Plant Compounds, Synthetic Hormones, The Human Being, and the Petri Dish


Plant “Estrogens” Wisdom

Natural constituents are more likely to act as modulators, or balancers, and are selective in their response based on the “estrogenic environment” they are in. This may be why studies have been conflicting and confusing on phytoestrogens, compounds found in plants that share structural and/or functional similarities to human hormones. I explained this in previous blog:

The most widely accepted mechanism of phytoestrogens are their actions on estrogen receptors (ERs), with a higher preference for estrogen receptor beta (ER-B) than estrogen receptor alpha (ER-a). For this reason, phytoestrogens have mostly been classified as selective estrogen receptor modulators (SERMs), blocking excess activity if estrogen is too high and mimicking estrogen effects if estrogen is too low. (1-3)

However, phytoestrogens’ activity isn’t selective for these estrogen receptors alone, and there is evidence that other receptors related to estrogen response may also be at play. (1-5) For example, it has been demonstrated that phytoestrogens can modulate aromatase activity (1, 6) and increase production of sex hormone-binding globulin (1,7), both affecting estrogen availability. This may be one reason why studies are so conflicting on benefits verses risks. (1-3)

In other words, these multi-mechanistic actions of these compounds will act differently than isolates alone on estrogen and androgen gene activity. Furthermore, they will also have a different mechanism based on the levels of hormones in the environment they are put in and how the effects are measured. I’ll explain this now.


The Estrogen Environment- Cell, Rodent, and Humans

In a 2002 study, Assessment of estrogenic activity in some common essential oil constituents, the authors explored that using different techniques to measure estrogenic effect demonstrated that what was found in petri dishes was different in yeast cells vs. human cell lines. Furthermore, these findings could not be extrapolated to mice (a living creature). I bolded the conclusion below, but left the abstract in full form for the curious:

Estrogenic responses have not only been associated with endocrine function, but also with cognitive function. Several studies have indicated that estrogen replacement therapy has favourable effects on cognition, and may have potential in the prevention and treatment of Alzheimer’s disease. Thus, ligands for the estrogen receptor, that have a better efficacy and adverse-effect profile than drugs currently available, require investigation. This study was undertaken to investigate the potential estrogenic activity of a number of essential oil constituents. Initially, estrogenic activity was determined by a sensitive and specific bioassay using recombinant yeast cells expressing the human estrogen receptor. At high concentrations, estrogenic activity was detected for citral (geranial and neral), geraniol, nerol and trans-anethole, while eugenol showed anti-estrogenic activity. Molecular graphics studies were undertaken to identify the possible mechanisms for the interaction of geranial, neral, geraniol, nerol and eugenol with the ligand-binding domain of the estrogen alpha-receptor, using the computer program HyperChem. Citral, geraniol, nerol and eugenol were also able to displace [(3)H]17beta-estradiol from isolated alpha- and beta-human estrogen receptors, but none of these compounds showed estrogenic or anti-estrogenic activity in the estrogen-responsive human cell line Ishikawa Var I at levels below their cytotoxic concentrations, and none showed activity in a yeast screen for androgenic and anti-androgenic activity. The potential in-vivo estrogenic effects of citral and geraniol were examined in ovariectomized mice, but neither compound showed any ability to stimulate the characteristic estrogenic responses of uterine hypertrophy or acute increase in uterine vascular permeability. These results show that very high concentrations of some commonly used essential oil constituents appear to have the potential to interact with estrogen receptors, although the biological significance of this is uncertain.

In an article assessing the safety of lavender in pregnancy, Robert Tisserand notes that in rats, lavender was not a uterine stimulant and has been used safely in childbirth for humans:

The research shows that lavender oil (L. angustifolia) is not a uterine stimulant. When used on the isolated rat uterus, it in fact reduced contractions (Lis Balchin and Hart 1999). And, lavender oil has no apparent adverse effects during childbirth. It was one of ten essential oils offered to 8,058 women in an 8-year study at the John Radcliffe Hospital in Oxford, UK. Aromatherapy did, however, reduce the need for pain medication. During the years of the study, the use of pethidine in the study center declined from 6% to 0.2% of women (Burns et al 2000).


The Most Important Thing to Remember About Essential Oils- EVER



A quality essential oil will contain a vast amount of therapeutic constituents that your body can “pick and choose” from in order to rebalance its physiological processes. This is the concept of essential oils “synergy” and is one of the most amazing things about essential oils. I refer to it as their “innate” healing power.

True, an essential oil will possess general properties based on its biochemical makeup, but factors such as our own genetic variances, microbiota diversity, and “internal environment” all influence its actions. (Read more about that here.)

I explained this more in part II of my epigenetic series. In it, I highlighted a study that reported on metabolomic markers that essential oils impacted. The researchers discovered that the biochemical pathways of individuals were differentially affected, with the same essential oils! (The metabolome is the collection of all metabolites from cellular processes in a cell, tissue, organ or organism.)

Essential oils seem to possess a “knowing” on exactly how they can help to balance the body in the way it needs.

I will be following up with more blogs that explore the “hormonal effect” of essential oils. I am currently compiling studies and assessing the conclusions. Previous blogs and background on using essential oils to support healthy hormones can be found below:


Additional Resources:

  • Robert Tisserand’s article which explains why lavender oil is not estrogenic and how studies extrapolating this have a major dosing issue. (see studies below for references)
  • Studies:
    • Uterotrophic assay of percutaneous lavender oil in immature female rats. (Int J Toxicol. 2013)
      • “Based on these data, lavender oil, at dosages of 20 or 100 mg/kg, was not active in the rat uterotrophic assay and gave no evidence of estrogenic activity.”
    • Consumer exposure to fragrance ingredients: providing estimates for safety evaluation. (Regul Toxicol Pharmacol. 2002)
  • Lindsey Elmore, the “Farmicist”, also has a quick summary of the latest study and her conclusions.
  • Lindsey Elmore’s FB video on the hormonal effect of essentials and the controversies. She explores how most of the concern for “estrogenic” effects are in vitro studies or with rodents in which essential oils were poured into their hysterectomized uteruses to measure contraction. (I’m sorry for the visual, I hate that this is done too!)
  • Essential oils are not without risk, but when used properly and with accurate dosage, they are very safe. Here are additional references to explore on essential oils safety:


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.)

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.

Thanks Pixabay.