There have been various reports suggesting that these two essential oils are endocrine disruptors as well as others that conclude the opposite. My own opinion on this matter is that there is more recent and conclusive evidence that these two essential oils are not endocrine disruptors.
The original study coming from the New England Journal of Medicine in February 2007 concluded that there is a link between these two essential oils and abnormal breast growth in young boys—called prepubertal gynecomastia. The information on the NIEHS site refers to the original study in the New England Journal.
Since then there have been other reports that disagree with their findings. For example the 2013 study in Reproductive Toxicology which used immature female rats with daily observations including viability, clinical signs, body weights, and body weight gains and found “no evidence of estrogenic activity”.
An opinion paper by Robert Tisserand published in March 2018 states that
“No connection was established between the in vitro work and the three cases, and the evidence for tea tree oil having an effect on prepubertal gynecomastia is non-existent. Phytoestrogens generally have a very weak hormonal activity, and it is implausible that the amounts of essential oil that enter the body from product use would have a significant effect.”
The most recent report restating that there is a connection appears to be utilizing the same information from the 2007 report and has no new metadata analysis or clinical studies cited.
As with all information relating to the health and well-being of our families or personal health everyone should proceed with caution and is encouraged to come to their own conclusions.
Feel free to review the information in the links below and respond with your own opinions.
How Lavender and Tea Tree Became Labeled As Endocrine Disruptors
Source: How Lavender and Tea Tree Became Labeled As Endocrine Disruptors – Earth Mama® Organics
Neither lavender oil nor tea tree oil can be linked to breast growth in young boys
Source: Neither lavender oil nor tea tree oil can… (PDF Download Available)
Tisserand, Robert. (2018). Neither lavender oil nor tea tree oil can be linked to breast growth in young boys.
Int J Toxicol. 2013 Mar-Apr;32(2):123-9. doi: 10.1177/1091581812472209. Epub 2013 Jan 28. Research Support, Non-U.S. Gov’t
Source: Uterotrophic assay of percutaneous lavender oil in immature female rats. – PubMed – NCBI
Full-Text Paper (PDF): Lack of evidence that essential oils affect puberty
Source: Lack of evidence that essential oils… (PDF Download Available)
Scientists studied chemicals in both oils and found they affected the cells in a way that would encourage abnormal breast growth
Source: New research shows lavender and tea tree oil may be making young boys grow breasts | National Post
The mission of the National Institute of Environmental Health Sciences is to discover how the environment affects people in order to promote healthier lives.
Source: Lavender and Tea Tree Oils May Cause Breast Growth in Boys
A new study lends further evidence to a suspected link between abnormal breast growth in young boys—called prepubertal gynecomastia—and regular exposure to lavender or tea tree oil, by finding that key chemicals in these common plant-derived oils act as endocrine-disrupting chemicals. The study results will be presented Monday at ENDO 2018, the Endocrine Society’s 100th annual meeting in Chicago.
Source: Chemicals in lavender and tea tree oil appear to be hormone disruptors | Endocrine Society
Original Article from The New England Journal of Medicine — Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils
Source: Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils | NEJM