5.Borax and Borax Powders. Some people believe that Borax can kill fleas. It is true that it can have natural insecticide qualities but it is also toxic to dogs and cats. Borax is a white, calcified mineral that comes off the Playas (dried seasonal lakes). It has many uses but mostly it is used as a mild detergent for laundry. There are several brands – the most talked about one is called "20 Mule Team Borax". Many people use it to kill fleas by spreading it on the carpet in its dry form (one to two cups per average sized room). Leave it on the carpet for two weeks without vacuuming to help to cover the different life cycles (e.g. eggs, larvae and adults). Some believe that by doing this household fleas will be eliminated for a year, but this is not true in our experience. Because it is toxic to dogs and cats, we recommend that if you do this you should keep your pet away from the Borax (especially as pets may walk through it then groom their paws and ingest this toxin). Leave the Borax down for an hour or so then vacuum it up (then you can allow your pet back into that area). Inhalation of Borax powder can also be irritating to your pet's lungs. Use it with care if you choose to use it at all. Also note that this Borax treatment does not prevent fleas from living on your pet and in the uncarpeted areas of your home.