Oxalic acid (H2C2O4) is an organic compound with acid properties that is highly soluble in water and in ethanol; it occurs naturally in plants, animals, humans, fungi, and microorganisms. It was one of the first known acids and was discovered in 1796 by the German scientist and pharmacist Johann Christian Wiegleb (1732–1800). It owes its name to wood sorrel (L. Oxalis acetosella). Since 1824, it has been produced chemically and is used in the food industry. This entry further describes oxalic acid and oxalates and then examines the associated health concerns and controversies related to the function and absorption of oxalic acid in the body and the formation of kidney stones.