Essential oils: How safe? How effective?

Use of an inhaled blend of lemon, eucalyptus, tea tree, and peppermint was associated with lower perceived stress and depression as well as better sleep quality.

In a randomized, double-blind clinical trial of 48 women, a cream-based blend of lavender, clary sage, and marjoram EO (used topically in a 2:1:1 ratio diluted in unscented cream at 3% concentration and applied daily via abdominal massage) reduced participants’ reported menstrual pain symptoms and duration of pain.³⁶ In a meta-analysis of 6 studies, topical abdominal application of EO (mainly lavender with or without other oils) with massage showed superiority over massage with placebo oils in reducing menstrual pain.³⁷ A reduction in pain, mood symptoms, and fatigue in women with premenstrual symptoms was seen in an RCT of 77 patients using 3 drops of inhaled lavender EO.⁴⁷

Labor. There is limited evidence for the use of EOs during labor. In an RCT of 104 women, patient-selected diffused EOs, including lavender, rose geranium, citrus, or jasmine, were found to help lower pain scores during the latent and early active phase of labor. There were no differences in labor augmentation, length of labor, perinatal outcomes, or need for additional pain medication.⁴⁸

Other uses

Antimicrobial support. Some common EOs that have demonstrated antimicrobial properties are oregano, thyme, clove, lavender, clary sage, garlic, and cinnamon.^49,50 Topical lemongrass and tea tree EOs have shown some degree of efficacy as an alternative treatment for acne, decolonization of methicillin-resistant Staphylococcus aureus, and superficial fungal infections.⁵¹ Support for an oral mixture of EOs labeled Myrtol (containing eucalyptus, citrus myrtle, and lavender) for viral acute bronchitis and sinusitis was found in a review of 7 studies.⁵² More research needs to be done before clear recommendations can be made on the use of EOs as antimicrobials, but the current data are encouraging.

Insect repellent. Reviews of the ­insect-repellent properties of EOs have shown promise and are in the public’s interest due to increasing awareness of the potential health and environmental hazards of synthetic repellents.⁵³ Individual compounds present in EOs such as citronella/lemongrass, basil, and eucalyptus species demonstrate high repellent activity.⁵⁴ Since EOs require frequent reapplication for efficacy due to their highly volatile nature, scientists are currently developing a means to prolong their protection time through cream-based formulations.⁵⁵

The bottom line

Because of the ubiquity of EOs, family physicians will undoubtedly be asked about them by patients, and it would be beneficial to feel comfortable discussing their most common uses. For most adult patients, the topical and periodic inhaled usage of EOs is generally safe.⁵⁶

There is a small body of evidence demonstrating that a variety of essential oils, most notably lavender, rose, and clary sage, may reduce dysmenorrhea symptom severity.

There is existing evidence of efficacy for a number of EOs, most strongly for lavender and peppermint. Future research into EOs should include higher-powered and higher-­quality studies in order to provide more conclusive evidence regarding the continued use of EOs for many common conditions. More evidence-based information on dosing, application/use regimens, and safety in long-term use also will help providers better instruct patients on how to utilize EOs effectively and safely.

CORRESPONDENCE
Pooja Amy Shah, MD, Columbia University College of Physicians & Surgeons, 610 West 158th Street, New York, NY 10032; pas2176@cumc.columbia.edu