How Lavender and Tea Tree Became Mislabeled as Endocrine Disruptors (Updated November 2022)

How Lavender and Tea Tree Became Mislabeled as Endocrine Disruptors

Over the years, there’s been a lot of confusion about lavender and tea tree essential oils as potential endocrine disruptors. But recently, the Breast Cancer Prevention Partners (BCPP) Science Department conducted a scientific literature review of the well-documented research on the safety of tea tree and lavender essential oils.

The results of the scientific literature review by BCPP

The BCPP Science Department reviewed the scientific literature for any documented associations between breast cancer and Tea Tree Oil (TTO) or Lavender Oil (LO) and found no documented evidence of an association between LO/TTO and breast cancer. Additionally, they found insufficient evidence to suggest that LO/TTO act as endocrine disruptors.
In the several publications examining the impact of TTO and LO exposure on endocrine disruption in pediatric patients, studies investigated health outcomes including prepubertal gymecomastia (breast development in boys) and premature thelarche (early breast development in girls). In a review of these studies, 11 cases of prepubertal gynecomastia or premature thelarche were described among four studies related to health effects of TTO and LO. The investigators concluded that the existing body of evidence is insufficient to confirm any link between LO/TTO and endocrine disruption in children. The review found no epidemiological evidence that TTO causes prepubertal gynecomastia or premature thelarche in children, and little to no evidence that LO is a likely causal agent.
Even though the use of essential oils has increased in prevalence in recent years, these cases remain extremely rare, as evidenced by the low number of cases in these studies (n=11). Epidemiological studies are needed to identify the incidence of endocrine disruption outcomes in pediatric populations with documented exposure to lavender essential oil. Any causal relationship that may exist between LO/TTO and endocrine disrupting outcomes likely involves some level of genetic or environmental predisposition.
In conclusion, there is no documented scientific association between LO/TTO and breast cancer or endocrine disruption in children and there is no evidence to contra-indicate use of LO and TTO currently.


The relationship between lavender and tea tree essential oils and pediatric endocrine disorders: A systematic review of the literature Complementary Therapies in Medicine

Pediatric exposure to endocrine disruptors and carcinogenic, mutagenic or reprotoxic substances by pharmaceutical forms intended for the cutaneous route: Regulatory provisions in France, in Europe, and state of the art of scientific knowledge 2022, Annales Pharmaceutiques Francaises

Prevalence of endocrine disorders among children exposed to Lavender Essential Oil and Tea Tree Essential Oils 2022, International Journal of Pediatrics and Adolescent Medicine

Effectiveness of lavender inhalation aromatherapy on pain level and vital signs in children with burns: a randomized controlled trial 2021, Complementary Therapies in Medicine

Special issue on aromatherapy: A low cost, low risk, complementary environmental therapy 2020, Complementary Therapies in Medicine

Eugenol, Isolated from the Essential Oil from Lonicera japonica Flower Buds, Could Increase the Oxidative Stability of Sunflower Oil in the Deep-Frying Procedure of Youtiao 2022, Processes

Evaluation of Placental Toxicity of Five Essential Oils and Their Potential Endocrine-Disrupting Effects 2022, Current Issues in Molecular Biology

View all citing articles

Earth Mama's Original Lavender and Tea Tree Oil Research Findings

Earth Mama's Original Research (Published April 2017)

From time to time Earth Mama® gets this question and time and time again we tell people: we’re not worried.

We’ll explain why below, but the short answer is this: We spent a great deal of time researching the reported issues with lavender and tea tree oil, and we have found no solid evidence that causes us to question the safety of either of these essential oils. They have been used externally for thousands of years by millions of people, our own research and that of other natural companies and associations conclude that they are safe.

But we understand why people are worried. So much confusion and misunderstanding came about from one questionable report from 2007 which asserted that lavender and tea tree oil wreaked hormonal havoc on young boys, thus causing them to grow breasts. Despite the lack of a large-scale study group, controls and the usual scientific practices the study was published and spread widely on the internet, causing much concern even today.

We at Earth Mama had never heard or experienced anything like those alleged reactions, and after scouring research and evidence based studies, we concluded that lavender and tea tree oil are as safe as we have seen them to be. In fact, their safety and benefits are so well-known to us, they’re the star ingredients in our Organic Diaper Balm, a product which is used in hospital NICUs even on fragile babies with Neonatal Abstinence Syndrome. The reputations of lavender and tea tree have been cleared in our book, but it’s time we helped set the record straight for everyone else.

The controversial study of Lavender and Tea Tree oil’s connection to gynecomastia

In 2007, the New England Journal Of Medicine released a study citing that lavender and tea tree oil “probably caused” prepubertal gynecomastia in three boys between the ages of five and ten. The authors stated that lavender and tea tree oil “possess weak estrogenic and androgenic activity,” but they concluded that this weak activity could be responsible for an imbalance in the estrogen and androgen signaling thus causing the boys to develop breasts.

This conclusion provoked alarm, however, there are issues with this study. These issues were so prominent that Robert Tisserand, longtime essential oil educator and researcher, co-wrote a letter with Christine Frances Carson of University of Western Australia, and Tony Larkman of Australian Tea Tree Industry Association. Here, they pointed out gray areas of the study, including;

  1. The products used by the boys were not noted, nor were their concentration of essential oils.
  2. The chemical composition of the essential oils studied were not disclosed.
  3. Because the chemical compositions weren’t tested or provided, there’s no way to tell if there were xenoestrogenic contaminants in the products' essential oils (or possibly in the products’ other ingredients).
  4. The constituents in tea tree oil are poorly absorbed by the skin (see the European Journal Of Pharmaceutics And Biopharmaceutics study for more info)
  5. The authors didn’t disclose studies with results which counter their findings, nor did they address the discrepancies.
  6. While weak estrogenic results may be seen in vitro (outside a living organism, ie. a test tube), it does not mean that these results can be replicated in vivo (inside a living organism). Much more testing would need to be done before one could conclude that tea tree oil or lavender oil are indeed endocrine disruptors.
  7. The plastic polystyrene trays used for lab testing contain xenoestrogenic compounds. Essential oils serve as a solvent, so it’s entirely possible the plastic lab trays could have contaminated the essential oil samples.

All things considered, the original study has some issues. But there are even more issues with this whole lavender/tea tree situation. Earth Mama’s founder, a nurse and herbalist, explains:

The doctors’ study did not take into account any other factors that may have been the cause of the gynecomastia. They didn’t look at their lifestyle, environmental exposure, or diet. Were they eating meat or drinking milk contaminated with growth hormone? Were other known endocrine disruptors like BPA in their water bottles or canned foods? Were they eating foods heated in plastics? The study did not ask these questions. Nor has there ever been, to my knowledge, a subsequent evidence-based study to evaluate the validity of the conclusion that lavender and/or tea tree essential oil are the cause of gynecomastia in boys."

Important Points on Gynecomastia

A 2014 review from the Indian Journal Of Endocrinology and Metabolism points out that the major cause of gynecomastia is hormone imbalance. Specifically, an increase in estrogen production and/or a decrease in androgen production. The authors of the study point out that the hormonal processes of puberty can cause gynecomastia (though puberty-related cases usually regress on their own within two years). In the event of non-pubertal gynecomastia, the scientists list a number of causes and contributing factors including: malnourishment, stress, drug medications, hyperthyroidism, hypogonadism, and other health issues.

Also, interesting: the review notes that humans are regularly exposed to hormonally-active compounds linked to gynecomastia. They’re contained in products like polycyclic aromatic hydrocarbons (PAH), pesticides, polychlorinated biphenyl (PCB), dichlorodiphenyl-trichlorethane (DDT), fungicides, cotinine, phytoestrogens, mycotoxins, bisphenol A (BPA), phthalates, alkylphenols, and metalloestrogens. Xenoestrogens are also found in car exhaust, cooked meat, chemical pollutants, milk, water, and cosmetic products. Long story short, our food and environment is subject to heavy contamination.

What We Know About Endocrine Disruptors

So, what’s the connection between gynecomastia and endocrine disruptors? To dive into that, we need to understand the endocrine system. When experts speak of the endocrine system, they’re referring to the hormones regulating the biological processes of our bodies. This system is involved with brain development, metabolism, and other processes, but the most notable endocrine system organs include the ovaries, testes, hypothalamus, pancreas, and the pituitary, adrenal, pineal, and thyroid glands. In essence, the function of the endocrine system is to regulate growth, metabolism, sexual development, and body function.

Now let’s talk endocrine disruptors. Endocrine disruptors are a problem because they can change or mimic hormones, inhibit hormone signaling, as well as increase or decrease hormone production. They also build-up in our fatty tissues.

This is concerning, because endocrine disruptors like xenoestrogens can lead to estrogen dominance. The organs of our reproductive system are very sensitive to hormones, so an excess of estrogen can lead to an imbalance. This imbalance is tied to issues like endometriosis, polycystic ovarian syndrome, irregular menstruation, prostate cancer, and male infertility.

The Journal Of Environmental And Public Health explains that the modern person is exposed to a variety of endocrine disruptors in everyday life. There are xenoestrogens in food additives and the plastics we use for food, antiandrogens are in pesticides and diesel exhaust, and antiestrogens are ever present in soy and chemicals. Scientists have also found these endocrine-disruptors in water and soil samples.

So, Are Lavender And Tea Tree Oil Safe?

In 2013, the International Journal of Toxicology published a study that tested lavender oil on lab rats. One group was given estradiol (a form of estrogen). The second group was administered lavender oil at either 20 mg or 100 mg per kilogram of weight. The third group, the control group, was given corn oil. Significant hormonal changes were determined by weighing the uterus of test subjects to determine estrogenic activity (the uterus responds to estrogen by increasing in weight). As expected, the group given estradiol had the greatest weight values of all three groups. However, the lavender group and the estrogen-free control group had comparable weight values. Based on this, the study concluded that lavender did not show signs of estrogenic activity.

Of further interest is a study published by International Journal Of Toxicology in 2008. Scientists tested linalool (lavender’s main constituent) on pregnant rats to see its effects on mother and fetus. Mother rats were given doses of either 0, 250, 500, or 1000 mg per kilogram of weight. The conclusion was that linalool was not a developmental toxicant, and it didn’t cause maternal or fetal harm. Even at daily ingestion of 1000 mg, it showed no adverse effects on mother or baby. That’s pretty amazing when you realize the doses of linalool given are equivalent to an adult ingesting 7 oz of lavender essential oil.

And what about tea tree oil? Well, if you remember the points addressed by Robert Tisserand in his letter, it was revealed that tea tree oil’s compounds are not readily-absorbed by the skin. And a study by the Journal Of Pharmaceutics And Biopharmaceutics showed that a 20% solution had just over a 1% absorption rate while a 100% solution was absorbed at 2-4%. With skin penetration so minimal, there isn’t anything to study in regards to estrogenic activity.

So what can we conclude from all this? Lavender and tea tree oil have not been proven to be endocrine disruptors. But studies on lavender essential oil suggest that lavender can help reduce anxiety and depression, promote better sleep, enhance healing of wounds, ease headaches and migraines, reduce scars and age spots, and more. Studies on tea tree oil demonstrate that it can be a natural and effective treatment for acne and fungal infections. It's also used as an antibacterial for housecleaning, natural hand disinfectant, and first aid.

If science is proving anything about these two herbs, it’s that they are versatile tools with a wide array of uses.


Prepubertal Gynecomastia Linked To Lavender And Tea Tree Oils The New England Journal Of Medicine

Gynecomastia: Clinical Evaluation And Management Indian Journal Of Endocrinology And Metabolism

Endocrine-Disrupting Chemicals: Associated Disorders and Mechanisms of Action Journal Of Environmental And Public Health

Environmental Exposure To Xenoestrogens And Oestrogen Related Cancers: Reproductive System, Breast, Lung, Kidney, Pancreas, And Brain Environmental Health

Uterotrophic Assay Of Percutaneous Lavender Oil In Immature Female Rats International Journal Of Toxicology

Evaluation Of The Developmental Toxicity Of Linalool In Rats International Journal Of Toxicology

Human Skin Penetration Of The Major Components Of Australian Tea Tree Oil Applied In Its Pure Form And As A 20% Solution In Vitro The Journal Of Pharmaceutics And Biopharmaceutics

How Lavender and Tea Tree Became Mislabeled as Endocrine Disruptors


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