"ESSENTIAL OIL MYTH : If you use a pure essential oil on your skin and it causes a rash or burn then its just your body detoxing.
FACT: They tell me this is a myth that quite a number of people are spreading but its hard for me to believe that there are people out there who are actually accepting this as a viable explanation. But I guess there must be a significant amount of people believing it because a number of you have asked me to address this. I suppose it comes from the desperate attempt for people to come up with some kind of positive explanation for any adverse reactions that natural products might cause us. I mean we all know that if something is natural that it must be good for us, right? Let's just think about this logically for a second. Let's imagine you rub poison ivy on your skin and you get a really bad rash. Is that just your body detoxing? Of course not. Come on people, if you get a rash or burn from putting something on your skin its because its IRRITATING YOUR SKIN. Furthermore, this "detox" explanation seems to ignore the very definition of what it means to detox. Generally, a detox reaction is a response that the body undergoes when it has something TAKEN AWAY from it. Think of the body of a drug addict "detoxifying" during the withdrawal process as he tries to get off the drugs. But in the case of using an essential oil on your skin we are ADDING something new to our bodies that your body has no prior experience with, any bad reaction could not logically be classified as a detox reaction. A rash or burn from an essential oil is basically your skin screaming at you "hey, stop that and stop it now!" This is why you should always do a patch test on a small area of skin and wait a while to see what happens before you go all crazy and start bathing yourself in an essential oil that you have not used before. I know many aromatherapist's recommend that you dilute the essential oils in a carrier oil for skin use. But no matter what concentration you use them at you should still do a patch test first for any new oils before moving on with the oil. Remember these are very concentrated solutions of organic molecules, let's be safe rather than sorry."
This information comes from Dr. Robert Pappas, an essential oil expert. The original source is his facebook page at Essential Oil University.