The main reason for halitosis is the enhanced evaporable amount of sulphur compounds in the exhalation, which originates in the oral cavity due to local protein fission. Oral bacteria hydrolyze proteins and further degrade amino acids, which leads to halitosis. In an alkaline environment, many bacterial species found in the oral cavity with their enzymes participate in the degradation of proteins and formation of evaporable sulphur compounds. The presence of bacteria in the oral cavity is associated with different chronic inflammations in the soft tissues of the oral cavity. Mouth rinsing agents, which contain essential oils, ensure the renewal of a normal microbiota in the oral cavity, decreases the quantitative amount of bacteria and products released by proteolytic bacteria. Bad breath was confirmed by measurements made by a portable sulphide monitor or halimeter (Interscan Corporation, Model RH-17E USA). The halimeter quantifies breath measurements in parts-per-billion (ppb) of sulphur compounds. Halimeter measurements of patients showed increased levels of sulphur compounds. Oral mouthwashes containing essential oils possess a typical antimicrobial activity, apparently, they do not form resistant microorganism strains, and they do not cause allergic reactions.