Only your body knows how you will respond to essential oils. Some people are sensitive. If you are a first-time user, have fair skin, or are using the oils with babies and children, take precautions. Dilute the oils using a carrier such as Seasame seed Oil or Coconut Oil. Suggested reading "Simple and Essential".

In random cases, essential oils applied directly to the skin may result in a rash. Some people may seem to experience a detoxification or flu-like symptoms when using the oils for the first time. Detoxification is the releasing of stored toxins from the body. People who have experienced difficulties using essential oils in the past may have been applying oils that were adulterated by either synthetic or natural means. Pure, raw, natural, therapeutic essential oils rarely cause problems when used correctly.

Essential oils are tested using a method known as chromatography, the science of separation. Mihail Semyonovich Tswett, a Russian botanist born in 1872, is considered the father or chromatography. He coined the term in 1906 when he described his experiments using a chalk column to separate the pigments in green leaves. "Chromatography" described the colored zones that moved down the chalk column. It is believed that he chose the name by combining the Greek words Kromatos, meaning color, and graphs, meaning written. It is possible that he named the process after himself since Tswett means color in Russian.

Prior to the 1970s, few reliable chromatographic methods were commercially available. Gradually, new techniques highly improved the separation, purification, and quantification of chemical compounds. Computers greatly improved the process and by the 1980s, chromatography was a commonly used analytical tool in chemical laboratories working with flavors and fragrances. Orange, Mentha oil, and eucalyptus were among the first oils to be tested in India.

Modern chromatography is generated by injecting a sample into a moving stream (mobile phase) which passes over a non-moving bed of particles (stationary phase). The stationary phase can be a solid or a liquid-coated solid that is packed into a column. The liquid coatings can be applied directly to a thin capillary column. Separation of the analytes is achieved by the analytes adsorbing onto the stationary phase by the mobile phase. the analytes that adsorb more strongly onto the stationary phase take longer to elute off of the column. There are several different types of chromatography. In GLC, or gas liquid chromatography, the mobile phase is a gas and the stationary phase is a liquid. For essential oils, GLC is the most common type of chromatography used. the resulting chromatogram is often referred to as the essential oil's "molecular fingerprint".

Chromatograms are of little or no use to anyone but a trained professional. This is why is necessary to have trustworthy experts to perform the test. They can bring attention to cases of adulteration with chemicals that would not normally be present in an essential oil.

Essential oils can also be adulterated with natural substances (i.e. lemon with d-limonene, ylang/ylang with linalool, peppermint with menthol, etc.). It takes an expert to interpret the GLC analysis and detect such "natural" adulteration. To the novice, the GLC trace may look acceptable because no synthetic adulterants are detected. Upon expert analysis, however, it will be seen that the ratios of the constituents are inconsistent and it will therefore be evident that the oil has been altered