Chemists are learning that smaller quantities of various compounds often have greater effects than previously expected.
In this report from the New England Journal of Medicine (via cnn.com) researchers have found that lavender and tea tree oils can act as estrogen mimics in certain cases:
Lavender and tea tree oils found in some shampoos, soaps and lotions
can temporarily leave boys with enlarged breasts in rare cases,
apparently by disrupting their hormonal balance, a preliminary study
While advising parents to consider the possible risk,
several hormone experts emphasized that the problem appears to happen
infrequently and clears up when the oils are no longer used. None of
those interviewed called for a ban on sales.
The study reported
on the condition, gynecomastia, in three boys ages 4, 7 and 10. They
all went back to normal when they stopped using skin lotions, hair gel,
shampoo or soap with the natural oils.
It's unclear how often this problem might crop up in other young children.
plant oils, sometimes called "essential oils," are added to many
health-care products, usually for their scent. The oils are sometimes
found in other household products or sold in purer forms. Tea tree oil
is sometimes used in shampoos for head lice.
The suspected effect
in this study is attributed to a chemical within the oils that the body
processes as it does estrogen, the female hormone that promotes breast
The findings were being reported Thursday in the New
England Journal of Medicine. The federally funded study came out of the
University of Colorado and the environmental health branch of the
National Institutes of Health. The findings were first released last
year at a science meeting.
The three boys were brought to their
doctors with overdeveloped breasts that looked like those of girls in
early puberty. They were sore in one case. For each boy, doctors could
tie the problem only to their use over several months of the
The researchers suspected that the oils
might be upsetting the boys' hormonal balance. So they did a series of
laboratory tests to check how these oils work within human cells. The
oils appeared to mimic estrogen and block the male hormone androgen.
product labels, the oils sometimes are listed by their scientific
names: Lavandula angustifolia (lavender oil) and Melaleuca alternifolia
(tea tree oil). Such products do not require government approval to be
sold unless they make specific health claims.
Marijuana and soy products also have been linked to gynecomastia.
Clifford Bloch, a hormone specialist in Greenwood Village, Colorado,
who treated the three boys, recommended that parents "be cautious" with
such products, especially for prolonged use. "I would not give these
products to my children," he said in an interview.
Bloch said he
also suspects the oil played a role in a handful of young girls he saw
for a similar condition, including a 17-month-old whose parents were
washing her bottles with a lavender-scented soap.
less worried. "It takes very little estrogen to cause gynecomastia in a
young child," said Dr. Richard Auchus, a University of Texas hormone
expert who knew of the study findings. "If they're getting it for a
brief period of time, that really shouldn't cause long-term problems."
the research did not pinpoint any specific estrogen-like compounds in
the oils or look for them in a range of products. Chemist Steven
Dentali, at the industry group American Herbal Products Association,
said that warning people to avoid such oils "is premature without the
additional basic research needed to bolster the case that the issue
here is both real and significant."
Gynecomastia is very common
in boys during the hormonal changes of puberty. But it also occurs as a
rare condition in younger boys, men, and girls before puberty.
Bloch, the study doctor, said it's unknown if such oils could hurt women with estrogen-fed breast tumors.
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