Question: is borax poisonous to humans?
Answer: Toxicity. Borax, sodium tetraborate decahydrate, according to one study, is not acutely toxic. Its LD 50 (median lethal dose) score is tested at 2.66 g/kg in rats, meaning that a significant dose of the chemical is needed to cause severe symptoms or death. The lethal dose is not necessarily the same for humans.