The research, conducted by scientists for the US National Institute of Environmental Health Sciences (NIEHS), suggests that a group of toiletry products, including gels, shampoos and lotions, appears to spark off a chemical reaction that causes a number of pre-pubescent boys to grow breasts.
Known as prepubertal Gynecomastia, it is a rare condition that affects the normal serum concentrations of endogenous steroids in other wise healthy boys.The study, centered on three boys aged seven to ten, found that Gynescomastia resolved in each patent following use of toiletry products known to contain the essential oils.
The research discovered that pure lavender and tea tree oils can mimic actions of estrogens and inhibit androgens, a combination that gives them unique endocrine disruption properties that increases estrogen levels, leading to an increase in breast size.
Speaking about the results, Kenneth Korach, from the NIEHS, recommended that parents of boys with the condition should check the ingredients in the cosmetic and toiletry products that they are using, just to rule out any link to these essential oils.
"Although we found an association between exposure to these essential oils and gynecomastia, further research is needed to determine the prevalence of prebutertal gynecomastia in boys using products containing lavender and tea tree oils," Korach said.
"Results of such epidemiological studies are important to tell us how strong the association is between topical application of the oils and the condition."
The researchers say they do not yet know which chemicals in the oils caused the changes. However, once identified, this evidence could lead to warning labels against children using such products.
However, the study also revealed t the researchers belief there will be no long term effects on the young boys' hormonal levels.