Dawn "Dish" Liquid, the Lie

Diatomaceous earth works well too especially if they infest your home. Do not apply directly to pets though.

https://www.petmd.com/dog/parasites/can-you-use-diatomaceous-earth-fleas
TIL (while searching if the word diatomaceous had ever been used here before because I would have bet that it hadn't) that there had been a DIY thread for pest control that's over 10 years old.