The losses of bee colonies has become a global problem, and one of the main reasons is the mite, Varroa destructor. It is a relatively new parasite which can cause the death of the whole bee colony if honeybees are not treated against Varroa. Beekeepers mostly use synthetic substances, but because of their harmful effects and increasingly frequent resistance, the use of natural compounds with acaracidal activity is promoted. Thymol is a monoterpene found in the essential oils obtained from plants belonging to the Lamiaceae family. It was found to possess acaracidal activity. Therefore, the aim of this study was to examine the influence of thymol on the feeding rate, mortality and enzymatic activity in the brain of adult bees. The activity of the two enzymes, the neurotoxic biomarker acetylcholinesterase (AChE) and the antioxidant glutathione S-transferaze (GST) was measured. Firstly, we conducted preliminary research to determine thymol concentrations and then we performed the main experiment with thymol concentrations of 0.05%, 0.5% and 1% w/w. Preliminary and main trial lasted for 7 days, bees were kept in wooden test cages, in the incubator and were exposed to the thymol orally. During the preliminary experiment we had two replicates for each treatment, and during the main trial three repeats for each concentration and control were conducted. During both experiments, dead honeybees were counted and removed every 24h and the mass of the consumed food was measured. After 7 days, the bees were sectioned and the enzymatic activity of GST and AChE was measured in their heads. The results of our research have shown that the exposure to thymol has no effect on honeybees feeding rate and that in concentrations up to 0.5% is safe for bees in terms of survival. Results related to the enzymatic activity of AChE and GST are inconsistent; by comparing the preliminary and main experiment there is a difference in the activity of these enzymes at the same concentrations of thymol. However, we have shown that thymol has an effect on AChE and GST activity in bees at 0.05% w/w, from which it can be concluded that thymol affects the cholinergic bee system and that detoxification has occurred.