Redness on the dog’s entire belly and the inside of its hind legs may be a sign of skin disease. You should take your dog to the pet hospital for examination and treatment in time. You should pay attention to the cleanliness of the dog’s living environment and regularly bathe and deworm the dog. During this period, the dog should wear an Elizabethan collar to prevent the dog from licking the medicine. In addition, do not take the dog out to avoid aggravating the dog's condition and infecting other pets.