Boric acid, which is an ingredient in laundry powders like 20 Mule Team Borax Detergent Booster, acts as an effective pesticide and will kill fleas. Boric acid is a desiccant that kills fleas by drying them out rather than poisoning them.
Sprinkling laundry powder around the house may not be a good solution for pet owners who want to relieve their furry friends of itchy fleas. Rather, these pet owners should look into using boric acid instead. While it is an effective pesticide, this desiccant may be harmful to mammals, including humans, dogs and cats, so care should be taken when using it as a pesticide.