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Essential Oils Q&A with Robert Tisserand


Essential Oils Q&A with Robert Tisserand

At Plant Therapy, one of our highest priorities is customer satisfaction. When our customers speak, we listen, whether it’s adding Oil of the Month oils to regular stock or more USDA Certified Organic essential oils. Recently, we’ve had customers ask for another Question & Answer round with leading industry expert Robert Tisserand. Ask and ye shall receive!

Robert Tisserand

Robert Tisserand has 47 years of experience in the essential oil industry. He has over 10,000 hours of speaking on aromatherapy and has written 3 books on the subject.

Plant Therapy: If you have an autoimmune disease, are there essential oils you need to avoid because they “stimulate” the immune system? Or is this a myth?

Robert Tisserand: This is not a total myth. I have said that Lavender Oil might be best avoided by people with multiple sclerosis. In this study, massage with Lavender Oil caused significant increases in CD4 and CD8 cells in breast cancer patients. The problem is that in MS, these immune cells tend to be higher than normal, so theoretically, Lavender Oil might exacerbate the condition.

This has never been known to happen, and in fact, it might not happen. This one piece of research is not definitive, and although these immune cells are generally high in MS patients sometimes they are low, and often the levels fluctuate.

There’s quite a bit of in vitro and animal research on essential oils and the immune system, but in general, we really don’t know much about what these oils might do either in a healthy human – arguably you don’t want your immune system “stimulated” – or in an immune-compromised person. So I think the best course of action is to use what you find works best for you, and not pay too much attention to the research.

person rubbing lotion on leg

PT: I read something about the dangers of generalized dilution rates. Basically, it said that spot treatments at higher dilution rates can, in fact, be safer than all over body treatments at lower dilution rates, because those lower rates can actually result in more total body EO absorption, and because there are many oils that actually require higher than a 1-2% dilution to be effective. What is your opinion on this?

RT: It’s difficult to discuss dilution and safety using words such as “higher” and “lower”, so let’s look at a specific example. Let’s compare applying a 2% dilution of EO over the whole body, to applying a 10% dilution to one leg. In a non-obese adult, the leg constitutes 18% of the total surface area. If we call this 20%, then we will end up with the same amount of oil absorbed, because we have a dilution five times more concentrated, applied to one-fifth of the body.

But the “higher dilution rates can be safer” argument assumes that safety is dependent on how much oil is absorbed into the body. This is true for oils with “internal” toxicities, such as neurotoxic, fetotoxic, hepatotoxic etc. However, for oils that may cause adverse skin reactions, this does not apply – risk depends on the dilution of the oil, not to the area of skin it’s applied to. So for a skin irritant oil, applying 10% to a smaller area of skin is most certainly not safer than applying 2% to the whole body.

person dropping essential oil bowl

PT: Can you explain the difference between purity and quality and describe the process for determining both?

RT: Purity is about whether an adulterant has been intentionally added to an essential oil to cheapen it and make it more profitable. Or whether an oil is contaminated with a substance that should not be there but was not added intentionally. Examples of contaminants include phthalates, which can come from any plastic material used in processing the oil. Plastics contain phthalates, and essential oils leach them out of the plastic.

It’s actually not unusual to find up to about 0.2% of a phthalate in some oils. This is clearly not an adulterant, as adding such a small amount would be pointless. It’s also not a safety concern. On the other hand, if you see 10% or 20% of a phthalate (phthalates are odorless) this clearly shows adulteration. Another example of an impure oil is one that is distilled from a mixture of plant material, instead of just one.

Quality is harder to define. But a poor quality oil might be quite old and oxidized, or it might have been distilled for too long (could contain small amounts of toxic constituents). Inappropriate distillation conditions can turn good quality plant material into poor quality essential oil. An oil might, for various reasons, have an unattractive constituent profile.

For example, Peppermint Essential Oil contains one main active constituent, menthol, and two neurotoxic compounds, pulegone and menthofuran. In this context, a good quality Peppermint Oil will be relatively high in menthol (over 40%) and relatively low in pulegone and menthofuran. High pulegone (over 1.8%) also gives Peppermint Oil a rather harsh odor.

Jar of aloe jelly with cuts of aloe

PT: Why are Aloe Vera Jelly and body wash safe to use as carriers?

RT: I’m not sure what’s behind this question, but there are concerns about the toxicity of whole leaf aloe vera extracts. Aloe extracts contain a dark yellow substance, aloin, which is an intestinal irritant when ingested, and which has been implicated in the development of intestinal cancers in lab animals.

In 2002, the FDA ruled that aloe laxatives are no longer GRAS. In theory, all aloe extracts produced in the USA are “decolorized”, i.e. the aloin is removed. This is certainly true of aloe extracts used in cosmetics, and no cosmetic grade aloe extracts have ever contained aloin. Aloin, if present, gives aloe vera extracts a brown-yellow tint.

If the question is about safely diluting oils, then aloe vera leaf extract is not a suitable diluent – it’s a very watery liquid, and essential oil will not mix in it. You need to use Aloe Vera Jelly, which has had other thickening agents added to it and also has a (necessary) preservative. This has a fairly thick gel consistency, one in which essential oils will mix (stirred, not shaken) and stay mixed.

parent and child practicing self care

PT: Is it important to use a natural lotion as a carrier or is any lotion safe? I get conflicting info on this.

RT: Whether certain cosmetic ingredients are safe or not is very much a matter of opinion (be wary of “toxins in your cosmetics” scaremongering), as is what constitutes a “natural lotion”. The word “natural” itself has no clear definition. What we do know is that a lotion has to contain an emulsifier, so that the water phase and the oil phase will combine, and it has to contain a preservative system (most preservatives are not single chemicals, they are synergies).

And, both emulsifiers and preservatives are generally at the synthetic end of the spectrum. Most emulsifiers are not particularly hazardous. Sodium lauryl ether sulfate (SLES) and some other sulfate emulsifiers have become notorious as they may contain traces of 1,4-dioxane, a probable human carcinogen. More on this here.

The role of a preservative is to kill bacteria and fungi that will grow in a watery, nutrient-rich environment, such as an emulsion. This action also tends to kill skin cells – to irritate the skin – and so preservatives and strong antimicrobials are often skin irritants. This also holds true for Thyme Oil, Oregano Oil, Clove Oil, and Cinnamon Bark Oil. In fact, these particular oils could possibly be used as cosmetic preservatives in some products.

The problem is, you would have to use about 2%, and, this would burn your skin. And your face cream would smell really strong and really nasty! The preservative issue is a complex one, and new preservatives are constantly coming on the market, but a completely natural, safe, all-purpose preservative (ie that will work in any product type) does not yet exist.

learning about essential oils with Robert Tisserand

PT: It was recently stated that whole milk (3.5%) is not a safe enough fatty carrier for baths, has there been a safe minimum fat % determined?

RT: For safety reasons, it’s really important to not put undiluted essential oils into a bath. If you have ever tried this, it was probably only once. Essential oils in the bath tend to be strongly irritant, and to places you really don’t want irritated. There is no kind of milk product that essential oils mix in, so none are really suitable for emulsifying essential oils in water.

The only type of substance that will properly mix essential oils in water is an emulsifier. A popular option for baths is Solubol (a mostly natural dispersant) use 4 drops to 1 drop of essential oil. You can mix essential oils in vegetable oil and then put in the bath – this will give you a floating (and somewhat greasy) bath oil.

Plant Therapy blue Tansy essential oil

PT: How concerned should one be about using blue or other oils either topically or through diffusion while on medications such as antidepressants?

RT: It would be prudent to avoid blue oils (anything high in bisabolol and/or chamazulene) if taking antidepressants, because there is a reasonable risk of drug interaction, and this would interfere with the action of the drug in the body, so it would not act as intended.

PT: Other people have told me that using heat destroys the therapeutic properties of the oil, is this true?

RT: It depends on how much heat, how it’s applied and for how long. “Destroying” therapeutic properties either means “burning” the oil by using extreme heat, or encouraging oxidation through moderate heat, but over a prolonged period of time (weeks or months). Using the normal types of vaporization simply vaporizes the essential oil molecules, but otherwise does not change them significantly.

Bottles and containers of beauty products

PT: Are PET/PETE1 safe to re-use with essential oil applications?

RT: I’m not sure by re-use. All plastics, eventually, break down in the presence of undiluted essential oils, it’s just a matter of time. With PET it can take a very long time indeed, but I don’t like the sound of “re-use”!

PT: Does diluting an essential oil in a carrier oil change the rate of oxidation for the essential oil? For example, if you dilute a short-lived citrus or conifer oil into a long-lived fatty carrier such as jojoba, will the oil oxidize more slowly than it would have if it remained undiluted?

RT: No, not meaningfully, the only kind of substance that will slow oxidation is an antioxidant. The most commonly-used one with essential oils is mixed tocopherols. This is useful if you are making an oil-based product that needs to last longer than a few weeks. Essential oils oxidize, but most fatty oils oxidize faster.

We would like to thank Robert for participating in this Q & A with our readers. If you have any questions or concerns, please email We look forward to hearing from you!