Borax has the same toxicity as table salt. People get it confused with Boric acid, which it is not. It isn't really a poison when used as a insecticide, it is sort of anhydrous. When a insect comes into contact with it (roaches, ants, fleas, etc) it pulls the moisture out of their bodies.
It isn't something you are going to want to eat, of course. It isn't something that you are just going to want to keep around the chins. But, cleaning with it isn't a problem. Using it for the fleas isn't going to leave anything toxic around...but keep the chins away from it because they may decide to consume a bit of it. It doesn't have any fumes or residue that will be harmful.
There are some countries that allow for it to be used as a food additive. (
www.borax.com) The company in the US that supplies it as the Borax that may be purchased at the grocery store doesn't recommend that at all.
On the internet there is a lot of weird information about Borax, but most of the negative comments say that it is boric acid. It isn't, so that information doesn't hold up for the Borax you would use for cleaning or for insecticides. It isn't safe to inhale, but most powdered substances aren't safe to inhale. It isn't a fine powder, so just take precautions to not get it up your nose.
