Essential Oil Toxicity

Many times we have questions come up concerning the use of oils, if they are dangerous, and what is the toxic level for various oils?
Most oils are really not dangerous if used in a responsible manner. In reality water, good old drinking water, can be toxic and will kill you if you drink too much. But in order to drink that much you would have to stick a hose down your throat and turn the hose on. Normal human reflexes would likely not allow you to "drink" that much.

But with oils, it is slightly different. Most people will have a problem if they are dehydrated. Their negative reaction is related to the degree of dehydration. Notable symptoms related to dehydration are; when the oils just set on the skin, the person develops a head ache, or the oil becomes offensive. Usually if the person will drink some water and rest for a while then those symptoms will go away. In extreme cases of when the person is sick they might vomit or develop a rash. In cases like this it is best to consult with a trusted person who knows about the oils or discontinue the use of that oil or use a lot less.
In working with animals you have to be a lot more sensitive to the aroma. If the animal does not like the aroma, then there isn't a lot you can do to "force" the use of that oil. A horse might kick you, a dog might bit you and a cat will scratch the day lights out of you. If they like it then they will usually cooperate with you. So the aroma is very important when working with animals. Then the size of the animal is very important, just like when you work with a child verses an adult. If too much is used on a child then they tend to behave more like an animal. An adult will use their brain and might over ride some unpleasant aromas or negative reaction because they know where they need to be going to with the use of the oil.
This is where we get into some of the myths about the toxicity of certain oils. Take Peppermint for example, many people will claim that this oil will kill a cat. Yes, it will if too much is used. The main chemical in this oil is Pulegone, which is a monoterpine. There were clinical studies done in  England, where half the the subjects were close to death. Not exactly what one would call a reliable study. They found an adult would have to take 31 ml., a child would need to take about 7 ml.,  and an animal like a cat would need about 0.40 grams per kg. of body weight to have a lethal dose. This test was only concerned with the one specific chemical, Pulegone. However, when it comes to the Peppermint Oil its self, the average Peppermint oil in its normal state, as you would use in Aromatherapy, the adult would need to take 350 ml., the child about 75 ml. and the animal would need to take 4.5 grams per kg. of body weight to have a lethal dose. So by this scale you can see why good old Peppermint could be toxic to a cat. If you were to put say 4 or 5 ml. on a 5 lb. cat, I am sure the liver would have a hard time processing that internally. But if using that much externally, then it wouldn't be as shocking on a short notice basis, but still lethal in the end.
So how do we select an amount for animals? In nature, a cat will usually not self medicate with a leaf type plant. They are a carnivore. In nature the first choice of self medication for a carnivore is a grass, not a leaf plant. A first choice for a cat would be to select a grass sourced oil. That is why you would not use a plant like Peppermint as a first choice. Although there is an herb and an oil that comes from Catnip. Cats love Catnip, which is in the mint family, therefore it is a leaf, but they usually don't eat it. They like the external effect of it. A note here, technically a blade of grass is a leaf. But I am using layman's language in referring to a blade of grass as not being a leaf as pposed to a leaf from a Peppermint plant.
Now when it comes to a dog, they are suppose to be carnivore, which I question, because of the high amount of grain used in dog food diets. They will do good with grain diets, not as good as with a meat diet, but none the less they will survive.  The big problem is the more grain in the diet, the bigger the dung heap. Higher levels of meat, the smaller the dung heap. Plus, I have observed healthy dogs that are vegetarians. So with dogs you can use different oils. You can use leaf oils on them and be just fine.
When it comes to humans then you have to consider a vastly different perspective. With kids, you have to approach them with more subdued aromas. Children are similar to animals, if it doesn't smell "Great" then they won't take it, no matter how much good it will do for them.
Lets get back to the oils that can be a concern. In the area of Aromatherapy we find all sorts of myths. In my research I have found that back in the 1800's they had oils all figured out from a medical approach. Then we go through the dark ages of essential oil use. Oils came back to life in the 1980's and they billed it as original material. At that time in the USA we had a lot of emphasis related to emotions. They had fancy terms from foreign sources that were billed as original material from a more enlightened sources. (Don't you just like my political correctness?).
Based on clinical research many of the oils such as Tea Tree and Eucalyptus are actually the more toxic ones.  But those that have used them can attest to how mild they are. On those oils an adult would have to take Tea Tree-148 ml. and Eucalyptus (globulus), which is suppose to be a spookier one, an adult would have to take 345 ml. I personally feel like  Euc. glob. is a very safe oil and from a clinical perspective the only safe one of all the Eucalyptus to be taken internally.
Many of the toxicity testimonies are related to this one issue, that of one event being tied to another event erroneously. This is where a lot of diagnosis is done by people that have no real understanding of what they are doing, yet they think they do. Here I want to cite a notation from a book by, "Valnet (1980 p. 11). It discusses the loss of one's eye brows and headaches in workers handling vanilla. Vanilla ice cream is produced, eaten and enjoyed without any ill effect. An essential oil may be both safe and toxic depending on the amount administered - a lot depends on the knowledge, skill and experience of the therapist.
For example, many have observed that while Lavender is sedative in low dose, a high dose can cause insomnia. The key to all of this is to know and understand what you have, what you are doing and be responsible. I have done a lot of experiments and noted the observations, and I am more and more convinced that many of these oils can be used externally in connection with carrier oils, and at the time of application, can be very effective and safe with out any toxic effects, short or long term.
So just some thoughts on the toxicity perspective.