Question: how does borax kill cockroaches?
Answer: How Borax Kills Roaches. For borax to work as an effective cockroach killer, the roaches have to eat it. ... Borax is technically sodium tetraborate and the “sodium” part penetrates the roaches' exoskeletons and dehydrates them. Cockroaches already dehydrate easily, which is why borax is so effective at killing them.