what serves as borax
While borax can kill fleas, never use it on your pup -- it's toxic to him. Michael Loccisano/Getty Images Entertainment/Getty Images. Sodium borate, more commonly known as borax, is a naturally occurring mineral salt of boric acid. This white, powdery substance frequently serves in detergents and pest control products.hile borax can kill fleas, never use it on your pup -- it's toxic to him. Michael Loccisano/Getty Images Entertainment/Getty Images. Sodium borate, more commonly known as borax, is a naturally occurring mineral salt of boric acid. This white, powdery substance frequently serves in detergents and pest control products.