The use of lavender and tea tree oils have long been suspected to be associated with abnormal breast enlargement in young boys.

Findings of a new study provide fresh evidence that supports this link.

Essential Oils

The plant oils, also known as essential oils, are added to many healthcare products often because of their scents. The oils can also be found in other household products and are sometimes sold in purer forms.

The tea tree oil is used in shampoos that treat head lice.

Male Gynecomastia

In a 2007 study, researchers reported the case of three boys between 4 and 10 years old with male gynecomastia, a condition marked by the enlargement of male breast gland due to hormonal imbalance.

The boys all went back to normal when they stopped using soap, shampoo, hair gel, and skin lotions that contain natural oils.

Now, researchers find new proof that adds weight to the suspected link between essential oils and abnormal enlargement of breasts in boys.

Can Mimic Actions Of Estrogens

Researchers of the 2007 study found that lavender and tea tree oils have estrogen-like and testosterone inhibiting-like activities. It means that they compete or disrupt the hormones that control male characteristics.

"The results of our laboratory studies confirm that pure lavender and tea tree oils can mimic the actions of estrogens and inhibit the effects of androgens," said Kenneth Korach, from the National Institute of Environmental Health Sciences. "This combinatorial activity makes them somewhat unique as endocrine disruptors."

Researchers now find that eight chemicals present in lavender and tea tree oil act as endocrine-disrupting substances, which interfere with the hormones and their actions in the body.

Chemicals In Essential Oils Show Estrogenic And/Or Anti-androgenic Properties

In a new study to be presented at the Endocrine Society's 100th annual meeting in Chicago on Monday, J. Tyler Ramsey, from the NIEHS and colleagues analyzed eight chemicals that are commonly mandated for inclusion in essential oils.

They found that four of these chemicals appear in both lavender and tea tree oils and the other four were present in either oil.

When the researchers applied these chemicals to human cancer cells in laboratory experiments, they found that all eight chemicals showed varying estrogenic and/or anti-androgenic properties.

They said that these changes were consistent with hormonal conditions in the body that stimulate gynecomastia in young boys.

"Our society deems essential oils as safe," Ramsey said. "However, they possess a diverse amount of chemicals and should be used with caution because some of these chemicals are potential endocrine disruptors."

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