Lavender Oil & Tea Tree Oil

I first became interested in the link between lavender and tea tree oil and signs of early puberty after reading an article in the New England Journal of Medicine (NEJM) related to the topic.  

The article I found, Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils, presents case studies of three prepubertal boys who developed enlarged breasts (gynecomastia). The boys' doctor, Dr. Clifford Bloch, discovered that they had all used lotions, creams, shampoos, styling products or soap with lavender or tea tree oil in them.  Once these products were stopped, the enlarged breasts went away.

In the NEJM article, the authors also present methods and results from in vitro studies they conducted, which confirmed "that lavender oil and tea tree oil possess weak estrogenic and anti-androgenic activities that may contribute to an imbalance in estrogen and androgen pathway signaling." The in vitro studies suggest that lavender oil and and tea tree oil, may not change the level of hormones in the body, but may interfere with their activity in the body.  The authors also wrote that they observed that the amount of exposure to oils seems to be important, i.e. there may be a threshold, below which there is no reaction, but above which, there is.

This made my head spin as I thought of all the products, which contain these oils. Lavender in particular seems to be in everything for kids, e.g., lotions, soaps, even in pure extract, given its purported soothing effect and pleasing smell. 

Here are some additional points for consideration:

1. I cannot comment on the scientific methods used in the in vitro studies. The findings about the boys, however, are based on 3 case reports.  As I discussed in an earlier post, case reports have the lowest strength of evidence, as they are descriptive (rather than based on statistical analysis) and are based on too few patients to be able to draw any real conclusions.

2. Still, even if the study findings are not conclusive and do not provide strong evidence, it can't hurt to be cautious. The NEJM article authors write:

"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."

3. The NEJM article was reported based on three boys in one doctor's clinical practice. As far as I know, no larger epidemiological studies have been done for boys, nor have any studies been done to determine whether these oils have similar effects in girls.

4. Even without those studies, however, we know that lavender & tea tree oil probably cannot explain why central precocious puberty (CPP) happens in some girls. The reason I feel confident putting this point so strongly is because central precocious puberty is triggered by the brain and we know that the level of hormones in these girls is affected, which differs from the tea tree oil and lavender oil responses.  (An earlier post, found here, explains how CPP happens.)

Therefore, my own conclusions about lavender and tea tree oils are that it probably cannot hurt to remove products with these from your homes if you have children -- , but I doubt that they will ever be found to be big contributors in the CPP mystery.  Again, what we really need, is a well-designed large-scale study to give us better answers.