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Lavender and Tea Tree Oils May
Cause Breast Growth in Boys
A study published in this week’s issue of
the New England Journal of Medicine suggests that repeated
topical use of products containing lavender oil and/or tea tree
oil may cause prepubertal gynecomastia, a rare condition
resulting in enlarged breast tissue in boys prior to puberty,
and for which a cause is seldom identified.
Researchers at the National Institute of Environmental Health
Sciences (NIEHS), part of the National Institutes of Health
(NIH), confirmed in laboratory studies what a pediatric
endocrinologist at the University of Colorado at Denver and
Health Science Center’s School of Medicine suspected after
diagnosing three of his young male patients with prepubertal
gynecomastia. The researchers found an association between the
use of products containing these oils and the rare disorder, but
cautioned more research is needed. At this point, the findings
are only applicable to young males with unexplainable enlarged
breasts who are regularly using products containing these
essential oils.
"We want to encourage doctors who may be seeing patients with
gynecomastia to ask their patients about the products they are
using. Patients with prepubertal gynecomastia may want to
consider reducing the use of products that contain these oils,”
said Ken Korach, Ph.D., chief, Laboratory Reproductive and
Developmental Toxicology at NIEHS and author on the
study.“Although we found an association between exposure to
these essential oils and gynecomastia, further research is
needed to determine the prevalence of prepubertal gynecomastia
in boys using products containing lavender and tea tree oils.
Results of such epidemiological studies are important to tell us
how strong the association is between topical application of the
oils and prepubertal gynecomastia”
The three otherwise healthy Caucasian boys, ages four, seven and
10 years, had normal hormonal levels when they were diagnosed
with gynecomastia by Clifford Bloch, M.D., in Colorado. All had
either used lavender-scented soap and skin lotions, or shampoos
or styling products that contained tea tree oil and lavender oil
as ingredients. In each case, several months after the suspected
products were discontinued, the gynecomastia had subsided or
resolved.
After Bloch discussed the cases with Korach, the NIEHS
researchers conducted experiments using human cells to determine
if the oils mimic the effects of estrogen, the female hormone
that stimulates breast tissue growth, or inhibited the effects
of androgen, the hormone known to control masculine
characteristics and inhibit the growth of breast tissue. The
researchers tested the ability of the oils to modulate or
inhibit gene expression.
“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 Korach. “This
combinatorial activity makes them somewhat unique as endocrine
disruptors.”
Bloch said the laboratory studies support his hypothesis. “Since
there was no identifiable cause for prepubertal gynecomastia in
the three patients we reported, we speculated that environmental
factors might be contributing to their condition. Together, the
case histories and NIEHS in vitro studies provide support for
our hypothesis that topical exposure to lavender and tea tree
oils likely caused gynecomastia in the three patients.”
The oils did not alter the levels of the usual forms of
circulating estrogens and androgens in the boys. “We do not
anticipate any long term effects on hormonal levels,” said Derek
Henley, Ph.D., the lead NIEHS author on the study. It is unknown
whether the oils have similar endocrine disrupting effects in
prepubertal girls, adolescents or adults.
“This study clearly demonstrates how clinical observations can
be supported by basic science research,” said NIEHS Director
David A. Schwartz, M.D.
These essential oils might now be considered endocrine
disruptors since they appeared to have caused an imbalance in
estrogen and androgen signaling. Endocrine disruptors are
naturally occurring compounds or synthetic chemicals that may
interfere with the production or activity of hormones of the
endocrine system leading to adverse health effects.
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