Milkweed Plant Can Cause Serious Poisoning

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The Asclepias genus is a group of perennial flowering herbs also known as milkweed due to their milky sap. There are over 200 species in the Asclepias genus that are native to Africa, North America, and South America. Monarch butterflies cannot survive without milkweed; their caterpillars only eat milkweed plants, and adult monarchs need milkweed to lay their eggs. The plant is most easily identified by its distinctive pod-like fruit containing densely packed seeds. When the fruit pods mature and turn brown, they burst and release the seeds. All parts of the plant contain toxic cardiac glycosides. The highest concentrations of cardiac glycosides are found in the plant's latex fluid followed by the stems, leaves, and roots. The plant is most toxic just before it reaches maturity.

Cardiac glycoside-containing plants have been used since ancient times for medical purposes. Milkweed has been used by indigenous peoples for swelling and rashes, diarrhea, and respiratory issues. However, cardiac glycosides have narrow therapeutic windows, meaning small changes in dosage can result in large differences in toxicity. Due to the prevalence of the plant, exposure to milkweed plants is very common. Unfortunately, even though milkweed is recognized as a poisonous plant, there are multiple websites that provide recipes for the preparation of fried milkweed pods, milkweed shoots, and milkweed elixir. Some of those websites state that the cardiac glycosides present in milkweed are water soluble, making milkweed safe to eat if cooked properly. However, there is no evidence that this is correct. Eating milkweed, even when cooked or boiled, is not recommended and is potentially very dangerous.

When swallowed, symptoms of milkweed toxicity usually appear within a few hours. Initial symptoms consist of stomach upset, nausea, vomiting, abdominal pain, diarrhea, weakness, lethargy, and confusion. Severe toxicity includes seizures, heart rhythm changes, and severe slowing of the heart rate. Milkweed is potentially poisonous to humans as well as animals. After grazing on milkweed in a field, sheep can develop difficulty walking, seizures, and death. 

The sap from the plant can also cause skin and eye irritation. If your skin comes into contact with milkweed sap, you should immediately wash the affected area thoroughly with soap and water. If someone experiences eye irritation after getting sap in their eye, gently rinse the eye with room temperature water for 10–15 minutes. If there are any persistent skin or eye pain or symptoms, seek medical examination and treatment.

If you suspect someone has been exposed to milkweed and is having a problem, check the webPOISONCONTROL^® online tool for guidance or call Poison Control at 1-800-222-1222.

Diana Pei, PharmD
Certified Specialist in Poison Information