In all the studies where toxicity of DEET has been desperately looked for, nothing has been found. Believe me, people have tried.
And it works.
As of a few years ago, I couldn't find anything without DEET in it that worked. There were rumors of Skin so Soft that didn't pan out and other products. I'm not familiar with Bite blocker.
DEET doesn't kill insects, it repels them. (It repels my SO, too, he hates that smell).

However - just an FYI, my bottle of DEET (Off) which I had stored in the pocket of the back door of my car leaked all over the back of the car, so much that is seeped out onto my bumper where it destroyed the 3M shield - it didn't affect any of the other sorts of plastic it hit. Could have been some other solvent in the Off formulation, not the DEET, but whatever it was was nasty to my bumper.