Are Essential Oils Toxic?

The following comment was made in a Facebook group for which I'm an admin. It was a lot to unpack in a reply, so I'm taking to my blog to answer in long form. The group member purports that anything with essential oils is toxic. So let's break this down and answer the question: are essential oils toxic? 

Her comment: 

I used to think [essential oils] were safe to use, too, until my body repeatedly taught me differently and began reacting to the highest quality, organic, pure brands that I sadly see being promoted as "non-toxic". I didn't immediately notice the effects, as they were cumulative and eventually showed up in the most uncomfortable ways. Removed the EOs, no more symptoms, brought them back, symptoms returned. Dots connected.

When EOs and/or products made with EOs are used in the shower/bath/laundry/etc., keep in mind that there are many different brand new chemicals being created once the chemical compounds in the EOs mix with other things, especially camphene that's found in most EOs - when camphene mixes with chlorine, found in most water supplies, it then creates toxaphene, which is a banned "forever" pesticide. That's for sure not a non-toxic option.

Also when EOs are oxidized, you then create several toxins like the benzene, formaldehyde, toluene, etc. that folks adamantly say they don't want to be around when they ditch the synthetically fragranced products, not realizing they aren't actually avoiding those (and many other) toxins by using EOs as an alternative. Again, not even close to being "non-toxic". The heavily marketed concept of purity indicates there's just a single pure chemical found in the bottle. Mega-companies, or small companies, or individuals wildcrafting their own are not adding the 200+ chemicals present in each bottle, these chemicals are what's being naturally extracted from the plants, no matter who makes them.

All of this info, along with much more research, can be found in the research-based book, Essentially Deadly: The Unspoken Dangers of Essential Oils, by April Graham.

Here's several links that may be helpful:

https://link.springer.com/article/10.1007/s11869-020-00941-4 "Essential oils emit many volatile organic compounds (VOCs), with some considered potentially hazardous. However, little is known about specific emissions from essential oils that make therapeutic claims for health and well-being. This study investigated VOCs emitted from 14 commercially available essential oils with therapeutic claims, such as beneficial for coughs, colds, flus, relaxation, sleep, tension, headaches, stress, or skin irritation..."

https://pubmed.ncbi.nlm.nih.gov/30546500/ "Fragranced consumer products, such as cleaning supplies, air fresheners, and personal care products, can have adverse effects on both air quality and health. This study investigates the effects of fragranced products on autistic individuals ages 18-65 in the United States, Australia, and United Kingdom..." "...Health problems can be severe, with 74.1% of these effects considered potentially disabling under legislation in each country. Further, 59.4% of autistic adults have lost workdays or lost a job, in the past year, due to fragranced product exposure in the workplace. More than twice as many autistic as well as non-autistic individuals would prefer that workplaces, health care facilities, and health care professionals were fragrance-free rather than fragranced. Results show that vulnerable individuals, such as those with autism or autism spectrum disorders, can be profoundly, adversely, and disproportionately affected by exposure to fragranced consumer products..."

https://www.sciencedirect.com/science/article/abs/pii/S0360132312001394 "This study aimed to examine the formation of secondary air pollutants (formaldehyde and secondary organic aerosols (SOAs)) in aromatherapy workplaces in which aromatic and volatile organic compounds were the dominant handling materials..."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6523335/ "Essential oils are natural products with a complex composition. Terpenes are the most common class of chemical compounds present in essential oils. Terpenes and the essential oils containing them are widely used and investigated by their pharmacological properties and permeation-enhancing ability. However, many terpenes and essential oils are sensitive to environmental conditions, undergoing volatilization and chemical degradation..."

https://pubmed.ncbi.nlm.nih.gov/35268817/ "Monoterpenes make up the largest group of plant secondary metabolites. They can be found in numerous plants, among others, the Lamiaceae family. The compounds demonstrate antioxidative, antibacterial, sedative and anti-inflammatory activity, hence, they are often employed in medicine and pharmaceuticals. Additionally, their fragrant character is often made use of, notably in the food and cosmetic industries. Nevertheless, long-lasting studies have revealed their toxic properties..." "...The presented review characterises in vitro and in vivo, the toxic character of selected monoterpenes (α-terpinene, camphor, citral, limonene, pulegone, thujone), as well as that of their original plant sources and their essential oils. The selected monoterpenes reveal various toxic properties among which are embryotoxic, neurotoxic, allergenic and genotoxic. It is also known that the essential oils of popular plants can also reveal toxic characteristics that many people are unaware of..."

https://www.sciencedirect.com/science/article/abs/pii/S1352231009006785 "Essential oils containing aromatic compounds can affect air quality when used indoors. Five typical and popular essential oils—rose, lemon, rosemary, tea tree and lavender—were investigated in terms of composition, thermal characteristics, volatile organic compound (VOC) constituents, and emission factors..." "...Some unhealthy VOCs such as benzene and toluene were measured at low temperature; they reveal the potential effect on indoor air quality and human health..."

https://pubmed.ncbi.nlm.nih.gov/15144499/ "Lavender (Lavandula angustifolia) oil, chiefly composed of linalyl acetate (51%) and linalool (35%), is considered to be one of the mildest of known plant essential oils and has a history in wound healing. Concerns are building about the potential for irritant or allergenic skin reactions with the use of lavender oil. This study has demonstrated that lavender oil is cytotoxic to human skin cells in vitro (endothelial cells and fibroblasts) at a concentration of 0.25% (v/v) in all cell types tested (HMEC-1, HNDF and 153BR)..."

https://pubmed.ncbi.nlm.nih.gov/27173437/ "In this article, contact allergy to, and the chemical composition of, tea tree oil (TTO) are reviewed. This essential oil is a popular remedy for many skin diseases, and may be used as neat oil or be present in cosmetics, topical pharmaceuticals and household products. Of all essential oils, TTO has caused most (published) allergic reactions since the first cases were reported in 1991..."

https://pubmed.ncbi.nlm.nih.gov/28614106/ "Synthetic fragrances and natural essential oils (EOs) are used in perfumery and found in various cosmetics. Essential oils are also increasingly used to promote wellness. In previous studies, the sensitization potential of some EOs has been identified; however, the current prevalence of sensitivity is largely unknown..." "...Testing to EOs may be important for detecting sensitivity not detected by FMs [Fragrance Markers] alone. In North America, M. alternifolia is an important and clinically relevant sensitizer often not detected by FM. In Europe, as well as in North America, clinical relevance is often difficult to evaluate because (1) labeling of EOs when used as fragrance is not mandatory, and (2) these mixtures may indicate sensitization to 1 or more of their individual constituents from other sources, including synthetic fragrances."

Like I said, it's a lot to unpack! Let's break this down claim by claim. 

Claim: Camphene combines with chlorine in water to create toxaphene 

There is no evidence to suggest that camphene from essential oils combines with chlorine in water to spontaneously form toxaphene. The pesticide toxaphene is indeed the result of the reaction between camphene and chlorine gas, however, it is only produced under specific conditions using UV light and catalysts. If it were to spontaneously form when camphene comes in contact with chlorine or chloride, catalysts wouldn't need to be used. (Source)

Claim: When EOs are oxidized, toxins like the benzene, formaldehyde, toluene, are created / essential oils form harmful VOCs

Benzene, formaldehyde, and tolulene indeed can be present in essential oils and not even necessarily due to degradation. They're natural compounds also present in our bodies, the environment, and plants. To say that essential oils are unsafe because these toxins are present doesn't consider the whole picture.     

When you isolate and concentrate these compounds, they are, of course, toxins. These three chemicals are all known carcinogens. But essential oils are complex mixtures with many different compounds that can counteract each other. Formaldehyde is naturally present in cruciferous vegetables which are well-documented for their anti-cancer properties. So just because a certain chemical is present in a mixture, doesn't mean the entire mixture is toxic. We can't just look at the presence of these chemicals and come to the conclusion that essential oils are toxic. We have to ask the big question: do essential oils cause cancer?  

The answer to that is, for the most part, no. We have to remember we're looking at hundreds of different plants and each essential oil is going to be different. Some oils do contain higher amounts of carcinogenic or possibly carcinogenic compounds without other compounds to counteract those effects. (see this article on which essential oils to avoid) But the most commonly used oils are not carcinogenic and many have anti-cancer properties. 

Peppermint essential oil, for example, has antioxidant properties. (Source, Source, Source)

Orange essential oil has known anti-cancer capabilities (Source)(Source)

Clove essential oil is being studied as a cancer treatment. (Source)(Source) 

Geranium essential oil is being studied for its chemoprotective effects (Source)(Source)

This study looked at the potential for cinnamon and related essential oils to fight lung cancer. 

Lemongrass essential oil also shows promise in treating lung cancer. (Source)

Citral-containing essential oils like lemongrass and lemon balm have shown anti-tumor activity, particularly in breast cancer. (Source) 

Essential oils are complex blends of compounds, so just because it has a particular minor constintuent that's toxic, it doesn't mean that the overall oil is harmful, as beneficial compounds can far outweigh the minor problematic compounds.

The poster seems to suggest that being around essential oils or smelling them is dangerous. Indeed some essential oils are toxic (see article link above) and one has to use essential oils in a safe manner. However, smelling some essential oils can be highly beneficial. 

This study found that lemon essential oil vapor induced an anti-anxiety and anti-depressant response.

This study found that certain salvia essential oils improved mood and cognitive function. 

This study found that bergamot essential oil reduced anxiety and pain in Alzheimer's patients. 

This study concluded that lemon balm essential oil can be a safe and effective treatment for patients with severe dementia. 

This review found that essential oils have numerous benefits to the nervous system, including "immediate changes in the autonomic nervous system and physiological responses such as pupil dilation, blood pressure, muscle tone, pulse rate, skin temperature, and brain activity. These body responses improve physical, mental, and emotional well-being after 15 min of inhalation."

Claim: Lavender essential oil is cytotoxic to skin

Lavender essential oil can indeed cause sensitization reactions with a history of improper or overuse. And some people can be allergic to it or develop allergies to the popular herb. However, for most people, when diluted and used judiciously, lavender essential oil has been shown to have clear benefits.

The study she cites above is an in vitro study - a study on cells in a petri dish, basically. What's more relevant to our health are in vivo studies, studies that have been carried out on humans or animals. (Human studies will be the most accurate.) 

This in vivo study on rats found that lavender essential oil accelerated wound healing and collagen production. 

This clinical trial on women who had undergone episiotomy procedures found that lavender oil helped reduce redness and irritation in the surgical site.

This study found that lavender essential oil massage could be beneficial for those with osteoarthritis. 

This study noted that lavender essential oil (when diluted properly) can even be beneficial in treating psoriasis. 

These stronger in vivo studies show the healing benefits of lavender oil when used appropriately. Certainly not cytoxicity to living human skin when we're looking at real-world scenarios. 

Bottom line: 

Essential oils are complex mixtures of aromatic compounds that must be respected, diluted, preserved, and properly used. And certainly there are instances where one would want to avoid anything fragranced, synthetic or natural. We respect these choices and experiences and offer a number of unscented products. Everyone has different mental associations with different smells and bio-individual responses to aromas. 

For years certain companies and their representatives have promoted unsafe use of essential oils and there are countless cases of people who have been harmed by improper essential oil use. This certainly has turned of many to essential oil use. However, when the right essential oils are properly diluted and respectfully used, they are not just safe but beneficial.