Burn balm, sleep aid, a soothing salve for bug bites – Dayle Harris has heard a hundred uses for the fragrant oil distilled from his fields of purple blooms. “I’ve even had people come in here (who) put it under their nose for snoring,” the Hood River, Ore., lavender grower said.

But making boys’ breasts grow? “I had never heard about this before in my life,” Harris said. Until this month.

A New England Journal of Medicine article tells of three young boys who showed up in a Colorado doctor’s office with gynecomastia, the medical name for benign-but-swollen male mammaries. Dr. Clifford Bloch traced the condition to the boys’ regular use of personal products made with lavender essential oil, which lab tests showed can act like the female hormone estrogen.

The discovery doesn’t mean lavender is dangerous: The condition is rare, and all the boys’ chests flattened out nicely when they stopped using the floral toiletries.

But the surprising addition of lavender oil to a growing list of chemicals that may interfere with human hormones has scientists as curiously excited as bees in a field of Twickle Purple.

And it’s sowing some interest and amusement, if not much worry, on lavender farms.

“I don’t think it’s anything that the lavender industry needs to worry about; most of our product is sold to women, not to men and boys,” said Curtis Beus, Washington State University extension director for Clallam County, Wash., capital of the blossoming U.S. lavender business.

While most of the world’s lavender is grown overseas and distilled into oil, dozens of boutique farms have sprung up in the Pacific Northwest in the past decade. Owners usually sow a few acres of plants, turning a profit by selling consumers dried bouquets and a range of consumer goods that have fueled an American lavender renaissance. The sweet-smelling oil scents lip balms, perfumes, massage creams, shampoos and soaps for bodies, dishes and laundry. The amethyst flowers fill sachets, “bath teas” and cuddly “comfort bears,” and flavor scones and tea cakes.

“We sell a lot to chocolate factories in New York and California,” said Joel Orcutt, whose Hood River Lavender Farms grows and distills organic lavender. “We keep finding new uses for it all the time.”

The plant’s main use is to smell good. But Orcutt said his customers also use the aromatic oil to end insomnia and clear stuffy noses. Herbalists primarily prescribe the plant for relaxation but know of several other uses, said Kimberly Windstar, a naturopathic doctor with the National College of Naturopathic Medicine in Portland, Ore.

“It stimulates digestion. It’s also used for the nervous system, soothing headaches and fevers … nausea and colic,” she said.

Acting like estrogen was a hidden ability, however, until a 4-year-old toddled into Bloch’s Colorado office about 10 years ago.

4-year-old affected

“Breast development in a 4-year-old boy is a very unusual finding. We don’t see it often. And something has to cause it,” said Bloch, a pediatric hormone expert with the University of Colorado.

The boy had normal hormone levels, and Bloch ruled out such serious problems as a tumor. He started eyeing the boy’s environment. The toddler’s mother said he wasn’t exposed to any unusual drugs or chemicals. But Bloch kept asking.

“Then the mother dropped the bomb: “I get this oil from a local homeopath. I put it on his chest every night to,’ as she put it, “fix his owies”‘ and keep him healthy, Bloch said.

Bloch persuaded the mom to take an owie break. The boy’s breasts shrank back down in two months. Bloch began looking for lavender behind other unexplained breast buds in young boys. He found the two other boys mentioned in the Feb. 1 journal article: a 7-year-old who used lavender soap and skin lotion and a 10-year-old who used hair gel and shampoo with lavender and tea tree oils.

The three boys in the study are all “clean cases,” untainted by other causes of gynecomastia, Bloch said. He also suspects lavender in several other cases of alarming breast growth in both boys and girls: One 17-month-old boy whose bottles were washed in lavender liquid soap “looked like he was in mid-puberty,” he said. One girl’s mother sprayed her bed linens with lavender every day: “This girl had breast development, and also some asthma,” Bloch said.

Convinced he’d caught the culprit purple-handed, Bloch contacted the National Institute of Environmental Health Sciences. Biologists there tested lavender essential oil and a relative, tea tree oil, on human breast cells that respond to estrogen. The oils hooked into the cells’ estrogen receptors. Interestingly, the oils also seem to interfere with androgens – male hormones that work through different biologic pathways, said Kenneth Korach, the biologist who led the tests.

“What is naturally occurring in those boys is that the androgen hormones are causing their breasts to regress,” Korach said. The lavender oils appeared to release that brake and step on the estrogen pedal, swelling the breasts: “We refer to it as a double whammy.”

Doctors are not sure just what to make of lavender’s busty nature. Many chemicals are known “hormone disrupters” – substances that can act like or block hormones – including the phthalates used to make plastics flexible and the banned drug DES, once given to some pregnant women. Windstar, the naturopath, wonders whether other chemicals in the soaps and balms the boys used might be the true cause of the condition.

Korach said it will take more tests to know how lavender compares to such known endocrine disrupters, though early tests of lavender oil showed only weak hormonal effects. There’s no evidence at this point that lavender will affect other hormone-sensitive conditions, such as some breast cancers – or that it would enhance the busts of women wanting more – though no research has studied those exact ideas.

“I think the take-home message is there’s a lot to learn about hormone disrupters,” said Sergio Ojeda, an Oregon Health & Science University endocrine expert.

Why lavender oils would swell only a few kids’ chests when so many people use them is a mystery.

“It may be a dose effect; you’d have to use it frequently or pretty intensely. There may be individual characteristics,” such as genetic mutations, Bloch said. “There are many questions, and we don’t claim to have all the answers.”

Korach plans to experiment and look for more answers. In the meantime, since the breast growth seems rare and reversible, the scientists said there’s no reason to shy away from your favorite lavender-scented shampoos or snacks. For Harris, that’s good news, for business and personal reasons.

“I have a 5-year-old son, and he’s in the lavender oil all the time,” Harris said. “So we’ll see.”