by Paige Wolf, Author of "Spit That Out! The Overly Informed Parents Guide to Raising Healthy Kids in the Age of Environmental Guilt" 

I remember when my son was an infant, back in 2009, I caught wind of a study that said lavender oil could cause “man boobs.” As a new mother concerned about literally everything, I started scouring bath products for lavender on the label and considered switching everything to a “safer scent.”

But then as I started doing the research for my book, I realized I was probably overreacting. 

It was a 2007 study in the New England Journal of Medicine that said lavender and tea tree oil contribute to gynecomastia, an abnormal breast tissue growth in prepubescent boys. The author of the (albeit controversial) study wrote, “The common use of products containing lavender oil, tea tree oil, or both by the three boys and the resolution of their gynecomastia within months after ceasing use of those products suggest that these oils may possess endocrine-disrupting activity that causes an imbalance in estrogen and androgen pathway signaling.” 

A 2018 study by National Institute of Environmental Health Sciences (NIEHS) further substantiated this evidence – lavender and tea tree oil do have estrogenic (estrogen-like) properties and anti-androgenic (testosterone inhibiting-like) activities. But the study was done by testing chemical isolates on in vitro cells, and it did not look at the results of direct undiluted oil use compared to application methods, such as applying the oils topically versus diffusing them in water.

Dr Rod Mitchell, pediatric endocrinologist at the Queens Medical Research Institute in Edinburgh was quoted as saying the study needs to be taken with a grain of salt. Well, he didn’t say that exactly, but he did say this: 

“At present, there is insufficient evidence to support the concept that exposure to lavender and tea tree oil containing products cause gynaecomastia in children, and further epidemiological and experimental studies are required.”

A few years ago, when I spoke with Dr. Ronald Stram, the director and founder of the Stram Center for Integrative Medicine, he concurred that theoretically, continued application of high doses of tea tree oil and lavender could result in such a condition. 

However, he said the use of these ingredients in conventional products is probably not something to worry about. 

As a general rule, never use undiluted oils, Stram says. He suggests keeping the concentration of both tea tree oil and lavender oil below 2% in children. (Hello Bello products use between 0.4% and 0.5% in its body care products.)

Remember – the dose can be the difference between pleasant and poison. And at a reasonable quantity, lavender can have wonderful effects like relaxation – something both parents and babies could use a healthy dose of!