Sulfur is an indispensable element of life. Plants manufacture its own amino-acids, which contain sulfur (cistin and metionin), by reduction of dissolved sulfates. The element is also a minority constituent of fats, corporal liquids and of the skeleton, being almost as abundant, in the organisms, as phosphorus.

In the human body the sulfur can be found of sulfates bound with organic compounds. The hydrogen sulfide, when in small concentrations, can be absorbed; however, in larger doses it causes death by breathing paralysis. The carbon disulfide can also be lethal but has a narcotic effect when ingested in reduced doses. The compounds of sulfur are not cumulative poisons. In spite of these effects, elementary sulfur is physiologically inert.