The use of thyme, because of its various antiseptic and antioxidant properties, is widely reported in gingivitis, stomatitis, and bad breath. You could even argue it’s like Listerine for dogs. A component of thyme, known as thymol, appears to inhibit growth of oral pathogens in the mouth and in combination with other essential oils, may reduce tooth decay. Thymol is one of the essential oils with antibacterial effects found in the human mouthwash, Listerine.