— Three young boys grew breast tissue after exposure to lotions and shampoos containing lavender or tea tree oil, researchers say.
It is not uncommon for boys to develop breast tissue during puberty or just after, but the boys affected by the plant oils were aged four, seven and 10.
The natural oils may be gender-bending chemicals mimicking effects of the female hormone, oestrogen, the findings suggest. The boys were otherwise normal, and lost the breast tissue within months of discontinuing use of the products.
Researchers who identified the oils as the cause of the abnormalities in the three pre-pubertal boys have warned parents and doctors to beware of the effects of any toiletry products containing the oils.
If consumers are concerned about exposure to lavender or tea tree oil, they should talk to their physicians, says Derek Henley of the US National Institute of Health Sciences labs in Research Triangle Park, North Carolina, US. Now that physicians are aware of the problem, they can document cases, adds Henley, whose team identified the oils as the probable cause in three affected boys.
In follow-up lab tests on breast cells, they confirmed that the oils act both as oestrogen mimics, and as suppressors of masculinising hormone signals. These are definitely the first substances to show a combination of oestrogen mimicry and anti-androgenic activity, says Henley.
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 warn.
Henley says that there are multitudes of products on offer containing the oils. But despite finding the connection, he says that the scale of effects remain completely unknown.
Its not fair to speculate on what the effects might be in girls, older women or older men, he says.
Because the boys were each exposed to the oils regularly for weeks, the researchers speculate that there might be a threshold dose for the effects to kick in. This, in turn, could depend on the concentration of the oil in the product, the duration of use, the frequency of use and genetic factors which make certain people, but not others, vulnerable to the effects.
Journal reference: New England Journal of Medicine (vol 365, p 479)
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