Research what herbs might help heart worm. I'm not sure if any herbs will help fleas. I'll see if I can find something. Be careful buying "natural" products for animals. Just like food isn't regulated or tested neither is topical products for animals. Many of these companies use essential oils that I know isn't extremely toxic to dogs and cats. Stay away from tea tree, lemongrass and anything very strong like those oils. Tea tree can kill a dog.