Calcium oxalate is a chemical compound that forms needle-shaped crystals. Large quantities are found in the painfully poisonous plant dumb cane. It is also found in rhubarb leaves, various species of Oxalis, and (in lower amounts) in spinach. Some kidney stones are caused by calcium oxalate.

All Arums typically have unique flowers, consisting of a pike of reduced male or female organs, or both, surrounded by a showy petal-like leaf, a bract, which is often colourful.

The toxic parts are the leaves. They contain calcium oxalate, a compound derived from oxalic acid, as well as enzymes which trigger the release of antibodies called histamines in the bloodstream of persons who ingest the leaves. Oxalates are needle-like crystals, which, when eaten, may pierce the mouth, throat and digestive tract as they pass through, causing, at the very least, intense discomfort.

Nonsoluble calcium oxalate crystals are found in plant stems, roots, and leaves. The stalk of the Dieffenbachia produces the most severe reactions. These needle-like crystals produce pain and edema when they contact lips, tongue, oral mucosa, conjunctiva, or skin. Oedema primarily is due to direct trauma from the needle-like crystals and, to a lesser extent, by other plant toxins (e.g. bradykinins, enzymes).

Even small doses of oxalate toxin is enough to cause intense sensations of burning in the mouth and throat, swelling, and choking. In larger doses, however, Oxalate causes severe digestive upset, breathing difficulties and - if enough is consumed - convulsions, coma and death. Recovery from severe oxalate poisoning is possible, but permanent liver and kidney damage may have occurred.

See also

• Oxalic acid

References