Sunday, January 8, 2012

Essential oils: Lavender and tea tree oil and gynecomastia

Can lavender essential oil cause boys to grow breasts (a condition called gynecomastia)? You probably heard about this a few years ago, so let's take a look at the case study (which you can find at the New England Journal of Medicine, February 2007 issue). A quick summary: This was a case study of three boys who had been exposed to lavender essential oil through body care products.

The conclusions of the case study...
Our in vitro studies confirm that lavender oil and tea tree oil possess weak estrogenic and antiandrogenic activities that may contribute to an imbalance in estrogen and androgen pathway signaling. Estrogenic or antiandrogenic activities have been reported for other essential oils and some of their monoterpene constituents. On the basis of the three case reports and the in vitro studies, we suspect that repeated topical application of over-the-counter products containing lavender oil or tea tree oil was the cause of gynecomastia in the three patients.

This report raises an issue of concern, since lavender oil and tea tree oil are sold over the counter in their “pure” form and are present in an increasing number of commercial products, including shampoos, hair gels, soaps, and body lotions. Whether the oils elicit similar endocrine-disrupting effects in prepubertal girls, adolescent girls, or women is unknown. Since gynecomastia is labeled idiopathic in approximately 10% of men, one might speculate that unidentified exogenous sources of endocrine-disrupting chemicals may contribute to the onset or progression of the condition, or both, in such patients. The results of our in vitro studies indicate a dose–response relationship in the estrogenic and antiandrogenic activities of lavender oil and tea tree oil, suggesting that susceptibility to gynecomastia or other manifestations of endocrine disruption may require exposure to a threshold dose of these oils. The 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 and should caution patients about repeated exposure to any products containing these oils.

Should you worry about whether not to use lavender and/or tea tree oil in your products? If you're basing your decision solely on this case study, I will refer you to the letters section of the Journal for the response from a small portion of the scientific community and encourage you to do a much more thorough job of researching this topic than I have done here. If you're just asking the question, I think this reminds us that we need to be really aware that essential oils aren't just about pretty fragrances but can have a physical effect on us. Essential oils are something most people would consider natural and they show up in all kinds of products, and it reminds us that we need to be very aware of what we're putting in our products regardless of the ingredient's origin.

An additional quick note thanks to a comment made by the Tony Larkman of the Australian Tea Tree Industry Association ( guess I have to make it clear that I don't think this was a good study and I don't think the conclusions were sound. People are complex creatures, and I don't think it's possible to come to the conclusion that these essential oils were the cause of the boys' physical issues with such little information. I thought my opinion would have been obvious from the context, but apparently I need to spell things out these days or I get nasty comments from people with financial interest in the ingredient. (If you want to dispute something I've written, here are some suggestions for how to do it and be nice about it.) 

I suspect Tony's new to the blog - he probably does a regular search for mean things written about tea tree oil and found what he thought was a slam of his product, instead of being a regular reader who would know about my perspective on science and how I write. He probably didn't bother to scroll back to December 3 to 6th to see all the nice things I've said about tea tree oil and all my suggestions for ways we could use his essential oil in our products. I'm guessing he probably didn't bother to familiarize himself with my blog before making a comment. 

His comment (which you can read in the comment section of this post): "It is intensely frustrating for the tea tree industry that this statement is still being promulgated in articles such as these without any evidence to back up the statement except poor science." 

A final thought...Does what he has written with his link and company information constitute advertising on my site? He could have written his opinion without putting that information in his comment. It wasn't essential to the post. What do you think?

And thus endeth the rant...

Join me tomorrow as we take a look at another essential oil!


p said...

For those concerned that lavender and tea tree might actually cause gynecomastia, here's a thorough response written by essential oil expert Robert Tisserand:

(You can download the article as a pdf from Tisserand's page here:

This study is so small, consisting of only three boys. And because it was a case study, the variable being evaluated, use of lavender and tea tree oil, wasn't isolated - so there are a great many possible causes of the boys' gynecomastia.

Susan, I very much agree with your point that essential oils are far more than pretty fragrances, and they have physical effects on the body. But I want to add that the same is true of fragrance oils, since their constituents - pthalates, synthetic musks, and so on - also have physical effects on us, including possible estrogenic activity.

Anonymous said...

Robert Tisserand's article refuting the link between gynecomastia and these essential oils is an excellent starting point if you want to research this further. It is worth noting that negligible amounts of tea tree oil were detected in one of the substances cited while there was no tea tree oil in the other two. How then can Henley et al link tea tree oil to gynecomastia?

One doctor in one town reports 3 cases in close succession and promotes as a scientific conclusion that Tea Tree Oil is a causative agent – even though only one of the 3 had any, and that a very tiny, exposure to Tea Tree Oil.

It is intensely frustrating for the tea tree industry that this statement is still being promulgated in articles such as these without any evidence to back up the statement except poor science.

Tony Larkman
Australian Tea Tree Industry Association

Susan Barclay-Nichols said...

Tony: My very subtle point - too subtle a point, it seems - is that the science behind this well publicized case study was insufficient at best and dubious at worst. I encourage the readers of this blog to read the letters I linked to above and do their own research because these were the points I was trying to make without being overt about it. I figured putting my opinion out there would mean others might not do their own research, and again, spoon feeding is really not my style.

P has shared great information with all of us, which is incredibly helpful. (Thanks, p!)

Tony - as someone unfamiliar with my blog and my writing style, can you advise where precisely in this post I promulgate any myths or bad science? Sharing information about a case study and quoting from it does not promulgation make. Can you point out where I state that I believe this summary of three case studies to be valid?

I do not appreciate the tone of your message or the implication that I am spreading misinformation. Please re-read the post and answer the questions I've posed to you. I look forward to your response.