About the Poison


The leaves of Rhubarb plants have poisonous acid in them, that can be very harmful to us, humans, as well as some animals.

Oxalic Acid, also known as "ethane diacid", has the chemical formula H2C2O4 and is a naturally occurring acid in some vegetables such as rhubarb, spinach, and cabbage. There is Oxalic acid found in all parts of the rhubarb plant, but it is found in very high levels in the leaves, making the leaves the poisonous part of a rhubarb plant.


Oxalic Acid is a molecular substance that offers no nutritional benefit to us and has to be excreted, in our case, it is excreted in the urine. If there is too much Oxalic Acid in the urine, it can combine with calcium to form calcium oxalate. This is found in kidney stones, so therefore too much Oxalic Acid can result in kidney stone formation. 

Although a large amount of Oxalic Acid needs to be ingested before it can cause death, even a small amount can cause sickness in humans. Ingesting the leaves of Rhubarb can cause any or all of these symptoms:

  • body aches

  • abdominal pain

  • mouth and throat pain

  • convulsions

  • low blood pressure and weak pulse

  • kidney problems and/or kidney stones

According to Miriam C. Benner, in a journal about pediatrics, a three year old boy entered the hospital and was complaining of abdominal cramps, diarrhea, and vomiting. This boy had eaten raw rhubarb leaves prior to his hospital visit, and he died after ten days in the hospital due to ulcers. After an autopsy it was shown that his ingestion of rhubarb, and the corrosives that may have been on the plant, may have been the sole cause of his death.

Oxalic Acid can also have a similar effect on animals, such as goats and pigs.



There are other uses of Oxalic Acid as well, other than finding it in plants. Oxalic Acid can reduce metal compounds and is commonly found in metal polishes and stain removers. It can also absorb oxygen and is therefore commonly found in bleach and bleaching agents.

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