What are essential oils?
Essential oils, which are obtained through mechanical pressing or distillation, are concentrated plant extracts that retain the natural smell and flavor of their source. Each essential oil has a unique composition of chemicals, and this variation affects the smell, absorption, and effects on the body. The chemical composition of an essential oil may vary within the same plant species, or from plant to plant. As an example of how concentrated essential oils are, 220 pounds of lavender flowers are required to produce approximately one pound of lavender oil. Synthetic oils are not considered true essential oils.
Have researchers studied essential oils?
Previous studies have shown that lavender and tea tree oil may act as endocrine disrupting chemicals (EDCs), which are natural or man-made compounds that mimic or oppose the actions of hormones produced in the human body. Also, clinical research found a possible link between the topical use of essential oils and the onset of male gynecomastia, or the development of breast tissue, in prepubescent boys. Since lavender and tea tree oil are composed of hundreds of chemicals, NIEHS scientists wanted to find out which of these chemicals displayed hormonal activity that could potentially lead to prepubertal gynecomastia.
What is NIEHS Doing?
NIEHS Lavender Oil and Tea Tree Oil Study
How did NIEHS researchers conduct the study?
The scientists applied lavender oil, tea tree oil, or eight of their chemical components to human cell lines in test tubes, known as in vitro experiments. They found that the compounds displayed a range of hormonal activities, which may stimulate prepubertal gynecomastia in boys.
Which essential oils and components were tested in the NIEHS study?
The researchers tested lavender and tea tree oil, as well as four chemicals commonly found in both: eucalyptol, 4-terpinenol, dipentene/limonene, and alpha-terpineol. These compounds were selected because the International Standard Organization mandated that they be included in both lavender and tea tree oils. The NIEHS research team also studied linalyl acetate and linalool, which are specific to lavender oil and alpha-terpinene and gamma-terpinene, which are specific to tea tree oil.
Do other essential oils contain these chemicals?
According to a chemical analysis of the chemical components of 93 essential oils, the chemicals selected in the NIEHS study appeared in at least 62 of them. The following list details how widespread these compounds are.
- dipentene/limonene – 90
- alpha-terpineol – 87
- linalool – 82
- 4-terpinenol – 80
- eucalyptol – 79
- gamma-terpinene – 79
- alpha-terpinene – 77
- linalyl acetate – 62
What age range are boys at risk for gynecomastia?
Male gynecomastia is a common clinical symptom observed during infancy, adolescence, and older age. Some physicians theorize that these times of major hormonal change may lead to the condition. However, prepubertal gynecomastia is relatively rare, since prepubescent boys have lower circulating hormone levels. Scientists suspect that this population may be more susceptible to hormonal changes and disrupting chemicals, which may lead to gynecomastia.
Is direct skin exposure the main link to male gynecomastia or can smelling or inhaling essential oils, as in aromatherapy, be linked, too?
The clinical cases have only described using essential oils on skin or topical exposure and not aromatherapy. In the NIEHS study, the team described whether topical exposure to the chemicals led to hormonal activity. Further studies are needed to determine if the same can be said about aromatherapy.
Are girls or women affected by lavender and tea tree oil?
No clinical cases describing abnormal breast growth in prepubescent girls or women have been reported. However, because breast growth is a natural process for pubescent girls, it is more difficult to determine whether lavender and tea tree oil have the same effect in females.
Are there differences between diluted essential oils and pure essential oils?
NIEHS researchers created different dilutions of the pure essential oils and the eight selected chemical components and tested their activity. They found as the dilution increased, the EDC activity of the oils and chemicals decreased.
Should the public discontinue the use of essential oils? Why or why not?
Whether a person uses essential oils is up to the individual. It isn’t a decision the scientists can make. The researchers want the public to be aware of the findings, since some essential oils and their components display hormonal activity and could be potential EDCs.
Stories from the Environmental Factor (NIEHS Newsletter)
- Botanical Safety Taken on by New Consortium (April 2020)
- Lavender Oil Linked to Early Breast Growth in Girls (September 2019)