Milkweed (genus Asclepias) is a familiar plant across many regions, widely recognized for its importance to monarch butterflies, which rely on it as their sole food source during their larval stage. While crucial for supporting these pollinators, milkweed also contains compounds that can be harmful to humans and animals. Understanding the potential dangers associated with this plant is important for safety.
Toxic Compounds in Milkweed
Milkweed’s toxicity comes from natural chemicals called cardiac glycosides, specifically cardenolides. These compounds are present throughout the plant, including stems, leaves, roots, and especially in the milky sap (latex) that oozes when broken. Cardenolides are potent substances that interfere with ion pumps, particularly the sodium-potassium ATPase, in heart and other tissue cells.
By inhibiting these pumps, cardenolides cause sodium and calcium to accumulate inside heart cells. This ion imbalance alters the heart muscle’s electrical activity and contractions. While similar to some heart medications, uncontrolled doses from milkweed can cause severe cardiac dysfunction.
Symptoms of Milkweed Poisoning
Ingesting milkweed can cause symptoms affecting the gastrointestinal, cardiac, and neurological systems. Initial signs often include digestive upset like nausea, vomiting, abdominal pain, and diarrhea, typically appearing within hours.
Beyond digestive issues, milkweed poisoning can impact heart function, causing decreased heart rate, irregular heartbeats (arrhythmia), and reduced blood pressure. More severe cases may lead to heart block. Neurological symptoms include weakness, drowsiness, dizziness, confusion, poor balance, yellow-tinged vision, headaches, muscle tremors, and seizures. Symptom severity depends on the amount ingested and individual susceptibility.
Factors Influencing Toxicity
Determining a precise toxic dose for humans is challenging due to several influencing variables. Different milkweed species contain varying cardiac glycoside concentrations. For example, common milkweed (Asclepias syriaca) is generally less toxic than non-native tropical milkweed or narrow-leafed varieties like whorled milkweed (Asclepias verticillata), which can be potent. Labriform milkweed (Asclepias labriformis) is among the most toxic species.
Toxin concentration also varies by plant part and maturity stage; the milky sap (latex) often has the highest cardenolide levels. The plant is most toxic just before maturity or during rapid growth. Individual factors like age, body weight, and overall health influence reactions, with children and sensitive individuals experiencing more severe effects from smaller exposures. Traditional preparation methods like cooking or drying do not reliably eliminate toxins; milkweed retains toxicity even when dried. While some boiling methods may reduce the toxic load, they do not guarantee complete safety.
Emergency Response and Prevention
If milkweed ingestion is suspected, immediate medical attention is crucial. Contact a poison control center (1-800-222-1222) or seek emergency medical services. For suspected ingestion, wiping or rinsing the mouth with a wet cloth and offering water can be helpful initial first aid.
For skin contact with the milky sap, which can cause irritation, thoroughly wash the affected area with soap and water. If sap gets into the eyes, rinse promptly with lukewarm water for 10-15 minutes, seeking medical evaluation if irritation or pain persists.
To prevent accidental exposure, educate children about not eating unknown plants. When handling milkweed, wear gloves and eye protection to minimize sap contact, and wash hands thoroughly afterward.