This is not an uncommon thing with hartz flea drops. Cats may loose hair (like my old cat) and that may be it or worse, like in your case. I am sorry about your kitten. If you have anyother animals never buy another Hartz product again. I have learned never to trust anything on the shelves for what they claim to do or assume that they are safe. All I can say is do research before trusting any pet care product.