The objective of this study was to compare the influence of four different concentrations of Salvia officinalis essential oil (EO) on animal health. A total of 50 laying strain chicks were randomly divided at the day of hatching into five dietary-treatment groups. Control group was given the basal diet (BD), the other four experimental groups contained BD supplemented with 0.1, 0.25, 0.5, 1.0 g S. officinalis EO/kg diet, respectively. 0.1 g/kg EO increased glutathion peroxidase activity (GPx) in duodenal mucosa, liver and kidney, phagocytic activity in blood (PA), transepithelial electrical resistance (TEER) in duodenal tissue and decreased malondialdehyde (MDA) concentration in plasma and liver. 0.25 g/kg EO increased GPx in liver, total antioxidant status (TAS) in plasma, PA in blood and TEER in duodenal tissue. Our results demonstrate that lower concentrations of EO improve animals' health status, and that it is necessary keep in mind the selection of sufficient concentration of EO used as animal feed additive.