What to do about a bald patch next to the dog’s mouth?

Hello, hair loss next to the dog’s mouth may be caused by mite infection or fungal infection. Since it is unclear whether the dog has scaling and other symptoms, take it to a vet for further examination to confirm the cause and give proper treatment.

If it is from a fungal infection, use antifungal medicine. If it is from mite or other parasite infection, deworm the dog promptly.