In January, 2007, the New England Journal of Medicine published a study by Henley et al linking lavender and/or tea tree oil to prepubertal gynecomastia (enlarged breast tissue) in boys. Since that time, several industry experts have presented evidence that lavender and tea tree oils cannot be linked to prepubertal gynecomastia. It is NAHA's position that until proven otherwise, these oils are safe for use as long as NAHA's Safety Guidelines such as proper dilution are followed.

In partnership with NAHA, the Franklin School of Integrative Health Sciences’ Research Department is leading a 3-part research project to investigate the proposed link between lavender and tea tree essential oils and endocrine disrupting outcomes, including prepubertal gynecomastia.