Posted by: Chris Maloney | August 19, 2015

Does Tea Tree Oil And Lavender Oil Cause Breasts In Little Boys? A Mayo Clinic Overreaction.

A patient emailed me concerned about using tea tree shampoo on her child. Here she is trying to do right by her children, and here’s the Mayo Clinic weighing in that tea tree oil can cause breasts in little boys. I was initially shocked, but there it is on the Mayo Clinic site.

“Avoid applying to the skin in boys before puberty, as this could cause reversible gynecomastia (growth of breast tissue) with tea tree oil and lavender oil.” (Mayo site here)

Goodness! How did I miss this dramatic hormonal action by tea tree and lavender oil? Rejoice, ladies, I guess we’ve got a cure for menopause. Forget your estrogen replacement, because clearly these essential oils are so powerful they can reverse the natural course of male puberty. 

But maybe you should hang onto your estrogen replacement for a moment. The Mayo Clinic information is based on a single article published in 2007, combining anecdotal reports from three patients. All three boys had gynecomastia (breast tissue growth) which occurs in 60 percent of boys during puberty. It is far more rare in boys before puberty, and 90% of those cases are unknown. So imagine the authors’ excitement at possibly finding a cause.

Reading through the report, a couple of things stand out. The three boys are four, ten, and seven.

Last time I checked, the ten-year-old is on the line for puberty, and after discontinuing the hair gel and shampoo with tea tree oil and the lavender products his breast bud development did not disappear, only decreased.

Of the other two boys, the four-year-old was getting a healing balm containing lavender to his skin, and his breast buds resolved four to seven months after mom stopped using the balm.

The third boy used: “lavender-scented soap and intermittent use of lavender-scented commercial skin lotions. The gynecomastia resolved completely a few months after use of scented soap and skin lotions was discontinued (personal communication from the patient’s family). His fraternal twin used the same skin lotions, but not the lavender-scented soap, and did not have any gynecomastia.”

OK, to recap, one boy reached puberty at ten, which may or may not have been sped up by any oil use. One boy had a cream applied that may or may not have affected breast buds that resolved seven months later. And one boy stopped using lavender soaps that his twin continued to use. Both twins now no longer have gynecomastia. Of the three, only one boy used tea tree at all, in combination with lavender. So why do we include tea tree at all?

Because our study researchers went on to test both tea tree and lavender on human breast cancer cell lines to look for estrogen-like effects. Never mind that human breast cancer cell lines do not hopefully have any equivalence at all to young boys’ healthy breast tissue. I think the results speak for themselves:

“Other components in these products may also possess endocrine-disrupting activity that contributed to the gynecomastia, but those components were not tested because we chose to evaluate only the component that was found in all the products used by the patients (lavender oil) and a chemically similar component that was found in some of the products (tea tree oil).

Our in vitro studies confirm that lavender oil and tea tree oil possess weak estrogenic and antiandrogenic activities…threshold might depend on several undefined factors, including the concentration of the oil in a product; the duration, frequency, and quantity of use of the product; and the genetic characteristics of persons exposed. Until epidemiologic studies are performed to determine the prevalence of gynecomastia associated with exposure to lavender oil and tea tree oil, we suggest that the medical community should be aware of the possibility of endocrine disruption” (complete study here)

So, is the testing of human cancer cell lines proof that the boys were affected? Not according to a follow-up study on tea tree oil that shows the compounds that are estrogenic are not absorbed. “The estrogenic potency of TTO was confirmed, but none of the bioavailable TTO constituents demonstrated estrogenicity.” (study here)

For lavender oil, the evidence is absolute for huge quantities: “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.” (study here)

But shouldn’t we avoid anything that might possibly cause estrogen issues? No. Doing the same cell line testing, researchers found that everything they tested on human breast cancer cells had either an estrogenic or anti-estrogenic effect. We’re talking about things like petroleum jelly and cocoa butter skin cream. (study here) So unless you want to forego all skin products, I’d have to say that simply being aware that it’s a possibility is all you need to do.

OK, so that brings us back to the Mayo Clinic’s website and recommendation. They’re citing a single, highly questionable, anecdotal study that has been debunked by more recent research. And they aren’t using the language that the researchers used. The researchers suspected that there might be a correlation. The Mayo Clinic added causation.

For comparison, let me argue the following: I want to market Tea tree oil as estrogenic, based on the anecdotal story of one boy who, while reaching puberty, developed breast buds while using a combination product that contained tea tree. For some reason, I think the medical community would have a problem with my “unfounded” claims. Yet the Mayo Clinic is prepared to advise complete avoidance on the same evidence. I think I’m going to have to stop using the Mayo as a reference source.



  1. […] Does Tea Tree Oil And Lavender Oil Cause Breasts In Little Boys? A Mayo Clinic Overreaction. […]

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