Essential oil of plants called Juniperus excelsa Bieb. (JE), Origanum minutiflorum O. Schwarz and P.H. Davis (OM) were used in this study. In order to determine experimental doses, LD50 values of essential oils were determined on mice. Taking into consideration the LD30 range, the experimental toxic doses were calculated for each rat (rat/kg). The toxic dosages thus determined were adapted to rats for active substances (rat/kg). Using commercially available pure virgin olive oil (VOO) as the solvent and diluting agent, OM oil (n=10), JE fruitoil (n=10), carvacrol (CRV) (n=10), VOO (n=10) and normal saline SF (n=8) were administered on the basis of 12 days into intraperitoneal (IP). Enzyme activities of Glucose-6-Phosphate dehydrogenase (G6PDH), malate dehydrogenase (MDH), Superoxide Dismutase (SOD), Glutathione-S-transferase (GST), Adenosine-deaminase (ADA) and Catalase were studied in isolates of kidney, brain and liver tissues. The data was statistically analyzed through Kruskal Wallis variance analysis. Elevated levels of GST and catalase have been found statistically important, as have both essential oil activities of OM and JE in the kidney tissue (p<0.005). All of the enzymes except the levels of ADA and SOD led to a statistically significant change in the brain and liver. There was sinusoidal hyperemia and capsular adhesion in the liver as histopathological were found to be statistically significant (p<0.005). It did not observe any important changes in the other organs. Findings were scored and analyzed by using x(2)(chi-square) test and Fisher's definite variance analysis.