Researchers think scented oils that are found in some shampoos, soaps and lotions can cause temporary breast growth in young boys, but only in rare cases.
A preliminary study released today says the oils appeared to disrupt the boys' hormonal balance.
The federally funded study comes from the University of Colorado and the National Institutes of Health and is reported in the latest edition of the New England Journal of Medicine.
Three boys, ages four, seven and ten, developed the condition while using products containing lavender and tea tree oils. All three were normal again when they stopped using the product with the natural oils.
Hormone experts advise parents to consider the possible risk. But because the condition appears to be rare and temporary, they're not suggesting a ban on sales.