> Oxalic acid has been used as a bleach and metal cleaner, although its use has declined in recent years. Poisoning in humans has resulted from inhalation of oxalate fumes, contact with the skin, and from ingestion. In the early 1920s oxalic acid was ranked among the three most common causes of poisoning in humans.

> Most oxalate-producing plants are palatable to livestock; therefore, the management of ruminants with access to these plants becomes critical.  Although sheep graze these areas extensively, poisoning only occurs under certain conditions. Under these conditions, however, more than 1200 sheep have been poisoned at one time. There are many cases where 100-800 head have died at one time. Deaths in numbers less than a hundred are common.

> The gross pathology observed is hemorrhage and edema of the rumen wall, in some instances ascites, and sometimes hyperemia of the abomasal mucosa occur. Histopathology includes calcium oxalate crystals in the wall of the rumen and in the tubules of the kidney. Hemorrhage has been observed in the rumenal wall and microhemorrhage may be seen in the medulla oblongata [brain].

> If the degradation ability of the rumen microorganisms is exceeded, then absorption of the oxalates takes place. It is likely, however, that some oxalate may be continually absorbed when an animal is
grazing oxalate-producing plants. Small amounts of absorbed oxalate are not harmful, but harmful results have been observed when animals are fed high levels (sublethal) of some oxalate-containing plants of the Oxalidaceae genera.

> The classical explanation of the cause of death in oxalate intoxication is hypocalcemia and/or uremia These undoubtedly have their effect, but they are inadequate to account for all the observed effects. Further investigation is needed on the effect of oxalate on energy metabolism, electrolyte metabolism, gastrointestinal function, and cardiovascular and neural function.

Lynn F. James (1972) Oxalate Toxicosis, Clinical Toxicology, 5:2, 231-243, DOI: 10.3109/15563657208991002

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