This investigation outlines how, from eleven commercial samples screened, three oils (one fresh, one oxidised and one, blended from commercial oils, mildly oxidised) were chosen by p-cymene content and peroxide index determination. These samples were then thoroughly defined by Gas Chromatography (GC), Gas Chromatography-Mass Spectrometry (GCMS) and physical constants to determine status with respect to the International Standards Organisation (ISO) standard for tea tree oil before being recommended for dermal penetration and other safety parameter investigations for the dossier.