Once your dog is diagnosed with fleas, they’ll need to receive multiple treatments to rid them of the infestation. If you’re using spot-on treatments, this may mean multiple uses before the infestation is completely eradicated. However, if you’re using oral flea medicine for dogs, you only need to give your dog a monthly dose to be protected year-round since they protect them for 30 days. It’s important to note that you should not give your dog flea medicine for cats or allergy meds for cats because they contain different ingredients that may be toxic.