It's important to note that even if you use a monthly flea preventative, you may still see occasional fleas on your dog. This is because fleas can jump from one animal to another, and even if your dog is protected, he or she can still be exposed to fleas from other animals. If you see fleas on your dog, you should treat him or her with a flea shampoo or spray to kill the fleas. You should also vacuum your home thoroughly to remove any fleas or flea eggs that may be present.