Essential oils could lead to breast growth in young boys. A new study from the National Institute of Environmental Health Sciences found that eight chemicals in some plant-based oils found in soaps and shampoos interfere with hormones. That can block testosterone while boosting estrogen. The study in particular looked at lavender and tea tree oil and found possible links to changes in puberty. Researchers caution that much more evidence is needed before making a definite link between oils and breast growth in children. The study is yet to be published.