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Lavender makes boys grow 'man boobs'

The lavender and tea tree oils found in some soaps, shampoos, hair gels and body lotions can produce enlarged breasts in boys, researchers report.

These plant oils were linked to abnormal breast development in three boys, which was reversed when they stopped using them, write Dr Clifford Bloch of Pediatric Endocrine Associates in Colorado, and colleagues.

They say their study, published today in the New England Journal of Medicine, suggests these oils can act in ways similar to the hormone oestrogen.

"This report raises an issue of concern, since lavender oil and tea tree oil are sold over the counter in their 'pure' form and are present in an increasing number of commercial products, including shampoos, hair gels, soaps, and body lotions," the researchers write.

"Whether the oils elicit similar endocrine-disrupting effects in prepubertal girls, adolescent girls, or women is unknown."

While it is very common for boys to develop temporary breast enlargement as they go through puberty, the condition is very rare in young boys.

Doctors call the condition prepubertal gynaecomastia, and often find no explanation for it.

The researchers found the condition in three otherwise healthy boys, aged 4, 7 and 10.

"I got wind of it because I was given a clue by a patient," Bloch says.

That case involved the 4-year-old "who was using absolutely nothing on his skin except a lavender oil preparation that his mother had obtained from a homeopath. She used to rub it on his chest and body every night" because lavender, in complementary medicine circles, is said to have healing properties.

Several months after the boy stopped getting the 'healing balm', his breasts returned to normal.

Meanwhile, Bloch then began to see lavender crop up in other cases, including the 10-year-old, who was using a hair styling gel and shampoo that contained both lavender oil and tea tree oil.

There was also a 7-year-old, who had been using lavender-scented soap and skin lotions.

In laboratory tests, scientists at the US National Institute of Environmental Health Sciences (NIEHS) found that both substances can mimic the action of the female hormone oestrogen.

They can also block male hormones that control both masculine characteristics and inhibit the growth of breast tissue.

But NIEHS researcher and co-author Dr Ken Korach is cautious about saying the essential oils cause the breasts to grow.

"Although we found an association between exposure to these essential oils and gynaecomastia, further research is needed to determine the prevalence of prepubertal gynaecomastia in boys using products containing lavender and tea tree oils," Korach says.