All pills can have reactions for all pets and people. With your donation Dede sends you this much needed pill for a flea battle. Dede loves this product as a fast way to get ahold of fleas. It's only for 24 hour fix. Let me know at check out in the notes section if you need a dog small, dog large, or cat pill. Then you need to do other things, see this newsletter Dede has about fleas to help guide you. https://www.myfavoritegroomer.com/april-2011