Borax and boric acid: toxicity and essentiality

   Boron is an essential trace plant nutrient. Although its exact function has not yet been established, deprivation of boron affects plant growth and in boron-poor soils, crop yields are diminished. An important application of borax is in borate fertilizers. In contrast, the toxicities of boric acid and borax to animal life are sufficient for them to be used as insecticides, e.g. in ant and cockroach control. Borax is also used as a fungicide; it acts by preventing the formation of fungal spores.

    The level of toxicity of borax is relatively low, but does cause some concern; e.g. borax and honey was, at one time, used to relieve the pain of teething in children, but this use is no longer recommended.