Boron in the elemental form is not toxic. The finely divided powder is hard and abrasive, and may cause skin problems indirectly if the skin is rubbed after contact. Trace amounts of boron seem necessary for good growth of plant lie, but large amounts are toxic. Boron accumulated in the body through absorption, ingestion and inhalation of its compounds affects the central nervous system. The symptoms are depression of circulation, vomiting and diarrhea, followed by shock, coma and a body rash.