I did a little paper test to test the authenticity of essential oils that I owned. So as per the test, if you put a drop of EO on a paper and leave it over night, the next morning you should not see any periphery of the area where it touched the paper. A pure EO completely evaporates leaving no residue behind. If you see a dark line, or patch on the paper, or the paper is oily, it indicates that the oil is blended with other oils. Of course, the residue will also depend on the kind of EO it is, as some oils are oilier than the others. Pls do your research before marking my words for it. The oils that I've tested are: 1. The Body Shop - Tea tree oil 2. Kama Ayurveda - Lavender essential oil 3. Kama Ayurveda - Ylang Ylang essential oil 4. Kama Ayurveda - Bergamot essential oil 5. Soulflower - Frankencense essential oil Conclusion - Of these brands, Kama Ayurveda was the purest and Body Shop is most diluted.