Redness and hair loss around the dog’s mouth may be caused by bacterial, fungal, and parasitic infections. You need to take the dog to the pet hospital for examination and treatment. At the same time, you must pay attention to the dog’s food hygiene and clean up the dog every day. Basin to avoid bacteria breeding for too long. Bath your dog regularly to deworm your dog. Do not use human body wash to bathe your dog, otherwise it will cause hair loss and skin diseases.