By Julie Edgar
WebMD Health News
Reviewed by Hansa D. Bhargava, MD
Sept. 6, 2016 -- Tea tree and lavender essential oils are popular ingredients in personal care and household products, including many aimed at children.
Latest Healthy Kids News
But can the ingredients, often promoted as "natural" alternatives, trigger abnormal breast growth in boys and girls?
A few small studies suggest that frequently using lotions, shampoos, styling gels, and even a certain cologne containing lavender and tea tree oils may cause breast growth in boys, also known as gynecomastia, along with breast growth in girls as young as 4 or 5.
Other studies have not reached the same conclusions, and the cases appear to be rare. In addition, scientific research into most natural products is scant. The FDA doesn't oversee essential oils unless they are intended for use in a drug, making it challenging to know how safe and effective these products are.
We asked a few experts to shed light on the research.
What the Studies Say
Lavender and tea tree oils are among the most commonly used essential oils used. Although research is inconclusive, lavender is often used for aromatherapy and calming lotions, while tea tree oil is promoted for acne, nail fungus, and other skin conditions.
In 2007, pediatrician Clifford Bloch, MD, noticed that three of his patients, boys ages 4, 7 and 10, had abnormal breast growth. After talking with their parents, he learned that one had been exposed to a lavender-based "healing" balm, another to a hair styling gel and shampoo with lavender and tea tree oil, and another to a shampoo and skin lotion with lavender.
Bloch ran tests looking for internal and external sources of the hormone estrogen that could potentially cause this to happen in the boys. He finally arrived at the cosmetic products the boys were using.
Lavender and tea tree oil have phytoestrogens, substances that mimic the hormone estrogen. Soy is a source of phytoestrogens, too.
Bloch's findings, published in the New England Journal of Medicine, led to a 2007 National Institute of Environmental Health Sciences (NIEHS) study that found both oils can act like estrogen. The study prompted the National Institutes of Health to issue an alert about lavender and tea tree oils potentially acting as endocrine disruptors -- something that interferes with the endocrine system -- in boys who regularly used products containing them.
Tony Starkman, CEO of the Australian Tea Tree Industry Association, calls the study "poor science." He said the amount of oils contained in the products was too small to have an effect.
"The fact is that tea tree oil was not present at all in two of the three topically applied products; therefore linking gynecomastia to tea tree oil is at best tentative and at worst incompetent," he writes in a statement to WebMD.
A year after the NIEHS study, the Research Institute for Fragrance Materials Inc. did its own study using rats. They found no evidence that lavender or tea tree oil affected hormones. In 2013, it completed a second study, again finding no effect.
More recently, pediatrician Alejandro Diaz, MD, published a study that blamed a lavender-based cologne popular in the Latino community, Agua de Violetas, for abnormal breast growth in two of his young male patients. He based the results on a chemical analysis of the cologne.
Aromatherapy expert and industry consultant Robert Tisserand, who lectures widely on essential oils, suggested that contaminants in the oils may have produced an estrogenic effect in Diaz's young patients.
"I think it's a real puzzle what actually happened. There are many metric tons of lavender and tea tree oils used in consumer products every year. We don't know how many are used for children, but what we see isn't an epidemic reaction. What we see represents a very small number of cases," Tisserand says.
The studies on lavender and tea tree oil are not conclusive, says Trevor Cates, ND, a naturopathic doctor who practices in Park City, UT.
"There are a lot of factors that can play a role (in breast growth and early puberty)," she says, and the amount of phytoestrogens in lavender and tea tree oil are too small to lead to gynecomastia. The boys may have been exposed to other environmental toxins that caused the problem, or may have a genetic predisposition to the condition, she says.
She says she would like to see a study that would ensure the oils were free from potential contaminants, such as pesticides or chemicals from packaging.
Diaz, of Nicklaus Children's Hospital in Miami, acknowledges that some children may have a genetic predisposition to gynecomastia that is triggered with enough exposure to lavender and tea tree oil. Or it may be that contaminants in essential oils somehow cause it. But he adds, "It is the responsibility of the industry that the products as sold are safe for human exposure."
Bloch says he continues to see about three to four cases of gynecomastia each year. In one case, a mother sprayed everything in the house with a lavender-scented spray, including the bed linens. When her son went to live with his father in a split custody arrangement, his condition disappeared. Bloch discovered a similar scenario when a 6-year-old girl came in with enlarged breasts.
In another case, a young boy stopped using a hair oil favored by his father -- a product containing tea tree oil – and his swelling breasts went back to normal.
"It's not in any way common," Bloch says. "I'm seeing it in a select number of kids."
In all the cases Bloch and Diaz documented, the children's breasts shrank when they stopped using the products.
Neither doctor said that consumers should avoid using products with lavender and tea tree oil.
Diaz says he doesn't have enough evidence to say they aren't safe. "In Miami, children are exposed to Agua de Violetas and most don't get gynecomastia. Nobody recommends against the use of soy, and it has estrogenic action."
Adds Bloch: "I'm reluctant to make statements where I don't have evidence. But when it comes to over-the-counter stuff, things that are 'natural,' you don't always know what you're getting. I think you should be careful with anything you put on your skin; there are many allergens in the environment. This is one hormonal effect of something we found."
SOURCES: Alejandro Diaz, MD, Nicklaus Children's Hospital, Miami Health System. Clifford Bloch, MD, Denver. Trevor Cates, ND, Park City, UT. Tony Starkman, CEO, Australian Tea Tree Industry Association. National Center for Complementary and Integrative Health: "Tea Tree Oil," "Lavender Oil." National Association for Holistic Aromatherapy. Diaz, A. Journal of Pediatric Endocrinology and Metabolism, January 2016. Henley, D. New England Journal of Medicine, February 2007. Politano, V. International Journal of Toxicology, March-April 2008. Politano V. International Journal of Toxicology, March-April 2013. Patisaul H. Frontiers in Neuroendocrinology, October 2010.
©2016 WebMD, LLC. All Rights Reserved.