A missionary friend is one of several readers who have written me recently about essential oils. He writes, ” Dr. Walt, we are discovering more and more of our friends getting into “essential oils” for various ailments. Have you researched these? I know that some of the compounds are probably in your alternative medicine handbook, but I wasn’t able to bring that with me here. Would love to get your quick thoughts on the issue (if you have any).” Well, of course I do:
The book I co-authored with Donal O’Matuna, PhD, Alternative Medicine: The Christian Handbook, does have a chapter reviewing aromatherapy, and this morning I published a blog on “Aromatherapy and topical aromatherapy oils — do they work for anything?” However, we did not do a review chapter on essential oils, as such.
So, where would I normally go to gather the most reliable, trustworthy, unbiased, and evidence-based site for up-to-date information on natural medications (herbs, vitamins, and supplements)? It is, as I often tell my readers, the subscription web site The Natural Medicines Comprehensive Database. However, they do not have a monograph on essential oils.
So, my back up site for this type of information is the Encyclopedia of Natural and Alternative Treatments. It is contained as part of the subscription web site ConsumerLab.com, a web site that I endorse but with which I have no financial ties (other than I pay a subscription fee like every other subscriber). I should note that I do not consider this encyclopedia to be as comprehensive as The Natural Standard, but I do not have access to it.
Anyway, the encyclopedia has a couple of nice reviews on the topical uses and the oral uses of essential oils. Since topical use is generally considered much, much safer, let’s start with that one (hopefully not breaking any copyright laws for what I believe is publicly available information):
Topical Use of Essential Oils
Tea tree oil, an essential oil from the plant Melaleuca alternifolia, possesses antibacterial and antifungal properties.30 It has been tried for various forms of vaginal infection, but the only supporting evidence for this use comes from an uncontrolled trial.31
There is slightly better evidence to support the use of tea tree oil for the treatment of athlete’s foot, fibromyalgia, and related fungal infections.32,33 One open study hints that oil of bitter orange, a flavoring agent from dried bitter orange peel, might have some effectiveness against athlete’s foot when applied topically.34
Topical essential oils might be helpful for alopecia areata, a form of hair loss that can occur in men and women. In a 7-month, double-blind, placebo-controlled trial, 84 people with alopecia areata massaged either essential oils or a non-treatment oil into their scalps each night for 7 months.35 The treatment oil contained essential oils of thyme, rosemary, lavender, and cedarwood. The results showed that 44% of the treatment group experienced new hair growth, compared to only 15% of the control group.
People with fibromyalgia experience muscle pain in many parts of the body. A pilot double-blind study found that topical application of a proprietary mixture containing camphor oil, rosemary oil, eucalyptus oil, peppermint oil, aloe vera oil, lemon oil, and orange oil could reduce fibromyalgia pain more effectively than placebo.59
Another study found that massage combined with the topical application of ginger and orange essential oils was no better than massage plus olive oil at relieving pain, reducing stiffness, or improving function in patients with osteoarthritis of the knee.63
One study in rats indicates that under some circumstances essential oils instilled into the ear may be able to penetrate the eardrum.53 While this supports the idea of treating otitis media (the typical ear infection of childhood) with herbal ear drops, it also raises concerns about possible harm to the middle ear.
Finally, for literally hundreds of essential oils, test tube studies show antimicrobial effects (activity against fungi, bacteria, and/or viruses).43 Presumably, essential oils are part of the plants own defenses against such organisms.
However, contrary to widespread claims, such studies do not indicate that these essential oils can work as antibiotics; innumerable substances kill microorganisms in the test tube but not when taken orally by people. (Bleach would be one good example!)
Here’s the Encyclopedia of Natural and Alternative Treatments article on oral use of essential oils:
Oral Use of Essential Oils
Eucalyptus is a standard ingredient in cough drops and cough syrups, as well as in oils added to humidifiers. A standardized combination of eucalyptus oil plus two other essential oils has been studied for effectiveness in a variety of respiratory conditions.
This combination therapy contains cineole from eucalyptus, d-limonene from citrus fruit, and alpha-pinene from pine. Because these oils are all in a chemical family called monoterpenes, the treatment is called essential oil monoterpenes.
For example, a 3-month, double-blind trial of 246 people with chronic bronchitis found that consumption of essential oil monoterpenes helped prevent the typical worsening of chronic bronchitis that occurs during the winter.24
Another study evaluated 676 male and female outpatients with acute bronchitis and found that essential oil monoterpenes were more effective than placebo.25
Essential oil monoterpenes are thought to work by thinning mucus, though they may have other effects.
Eucalyptus oil alone may be helpful for respiratory problems as well.
In a double-blind trial, 32 people on steroids to control severe asthma (steroid-dependent asthma) were given either placebo or essential oil of eucalyptus for 12 weeks.42 The results showed that people using eucalyptus were able to gradually reduce their steroid dosage to a greater extent than those taking placebo.
In another study, eucalyptus oil proved helpful for the treatment of “head cold” symptoms (technically, nonpurulent rhinosinusitis).47 In this double-blind, placebo-controlled study of 152 people, use of cineole at a dose of 200 mg three times daily markedly improved cold symptoms as compared to placebo.
A double-blind, placebo-controlled study of 39 people found that an enteric-coated peppermint-caraway oil combination taken 3 times daily by mouth for 4 weeks significantly reduced dyspepsia pain as compared to placebo.26 Of the treatment group, 63.2% of participants were pain-free after 4 weeks, compared to 25% of the placebo group.
Similarly, results from a double-blind comparative study of 118 people suggest that the combination of peppermint and caraway oil is comparably effective to the standard drug cisapride, which is no longer available.27 After 4 weeks, the herbal combination reduced dyspepsia pain by 69.7%, whereas the conventional treatment reduced pain by 70.2%.
A preparation of peppermint, caraway, fennel, and wormwood oil was compared to the drug metoclopramide in a double-blind study enrolling 60 people.28 After 7 days, 43.3% of the treatment group was pain-free, compared to 13.3% of the metoclopramide group.
Silexan is a capsule that contains a preparation of lavender oil. Two hundred and twenty-one adults diagnosed with having an anxiety disorder were randomized to receive 80 mg a day of silexan or placebo for 10 weeks.65 Those who were in the treatment group had a reduction in their anxiety, slept better, and did not have any unwanted side effects compared to those receiving the placebo.
Lorazepam (Ativan) is a common medication prescribed to treat anxiety. In one study, adults with generalized anxiety disorder were randomized to receive lorazepam or silexan.67 At the end of the 6-week period, silexan was as effective as lorazepam in reducing anxiety symptoms.
Again, silexan does not appear to have any side effects and, unlike lorazepam, it does not have the potential for abuse.
Other Oral Uses for Essential Oils
One study found preliminary evidence that a complicated mixture of essential oils (taken by gargle or mouth spray) might be helpful for reducing snoring symptoms.48
A thorough review of 11 randomized, controlled trials found that the use of mouth rinses containing essential oils is effective against gingivitis and dental plaque formation when used in combination with regular oral hygiene.62
SAFETY ISSUES: Essential oils can be toxic when taken internally, producing unpleasant and even fatal effects. While toxicity studies have not been performed on some essential oil products, the maximum safe dosages remain unknown for many.36
Infants, children, seniors, and people with severe illnesses should NOT use essential oils internally except under the supervision of a physician; healthy adults should only use well established products (such as peppermint oil) for which safe dosages have been determined.
Again, inhaled or topical use of essential oils is considered much safer than oral use. However, allergic reactions to inhaled or topical plant fragrances are not uncommon.37,38
Furthermore, when applied to the skin, some essential oils might also promote sunburning (photosensitization), raise the risk of skin cancer, or be absorbed sufficiently to cause toxic effects.39 In addition, one report suggests that a combination of lavender oil and tea tree oil applied topically caused gynecomastia (breast enlargement) in three young boys.55
Hope this helps.