Fungus on the Nails Toenail fungus can be difficult to eradicate, but because it is an infection, the antiseptic characteristics of mouthwash can help to eliminate it. The active ingredient in mouthwash that kills fungus is chlorhexidine, which can be used to treat fungal nails. Mouthwash can also help keep fingernails and toenails healthy by removing any bacteria that may live in the space between them. This can help prevent the development of fungal infections such as nail fungus. Using mouthwash daily is a good way to ensure that you are cleaning your teeth and gums regularly. This will help reduce the amount of fungus that can grow if you have poor oral hygiene. Mouthwash should never be used as a replacement for professional care of your nails or teeth. If you are suffering from nail fungus, we recommend that you see a doctor to determine the cause of your symptoms and receive proper treatment. If you are experiencing pain when chewing food, have black spots on your nails, or feel warm or itchy around your nails, then you might have a fungal infection and need to seek help.