Common milkweed Toxic?

Updated 2026-03-06| 3 min read| 2,698 found this helpful

All plant parts are toxic, especially the milky sap, which contains cardiac glycosides and bitter steroid glycosides.

Ingestion is fatal for horses, cattle, and sheep when other forage sources are scarce, and it is severely toxic to birds.

Treatment relies on prompt decontamination and symptomatic supportive care after exposure.

FAQ

Is Common milkweed toxic to Humans?

No specific human symptom data documented; large ingestion may cause gastrointestinal irritation and abnormal cardiac function. (Low)

Is Common milkweed toxic to Cats?

No specific feline symptom data available; ingestion is suspected to cause vomiting, diarrhea, and potential cardiac rhythm disruptions. (Low)

Is Common milkweed toxic to Dogs?

No specific canine symptom data available; ingestion may lead to gastrointestinal distress and possible cardiac abnormalities. (Low)

Is Common milkweed toxic to Horses?

Ingestion is often fatal; symptoms may include tremors, irregular heartbeat, respiratory failure, and sudden death. (Severe)

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Toxicity Details

Humans

Low

No specific human symptom data documented; large ingestion may cause gastrointestinal irritation and abnormal cardiac function.

Cats

Low

No specific feline symptom data available; ingestion is suspected to cause vomiting, diarrhea, and potential cardiac rhythm disruptions.

Dogs

Low

No specific canine symptom data available; ingestion may lead to gastrointestinal distress and possible cardiac abnormalities.

Horses

Severe

Ingestion is often fatal; symptoms may include tremors, irregular heartbeat, respiratory failure, and sudden death.

Toxicity Snapshot

Toxic PartsAll parts of the plant, especially the milky sap

Exposure RouteIngestion is the primary toxic exposure route; direct contact with milky sap may cause skin or eye irritation in sensitive individuals.

Toxic CompoundsCardioactive cardenolides (α- and β-asclepiadin); Steroid glycosides with saponin-like properties (Asclepiadaceae bitter principles)

First Aid & Prevention

First 30 Minutes

• Induce vomiting immediately if the patient is conscious and has ingested the plant within the last 15 minutes.
• Rinse the mouth thoroughly with clean water to remove residual plant material.
• Wash any skin exposed to milky sap with mild soap and cool running water.

Contact Vet Immediately

• If a horse, cattle, sheep, or bird has ingested any quantity of the plant.
• If symptoms like vomiting, lethargy, irregular heartbeat, or breathing difficulties appear after exposure.
• If milky sap has come into contact with eyes or broken skin, and irritation persists.

Prevention

• Remove common milkweed from pastures and yards accessible to grazing livestock, horses, and pet birds.
• Avoid planting the species in areas where unsupervised pets or young children may encounter it.
• Educate forage managers to identify and eradicate the plant to reduce livestock poisoning risk.

Treatment & Prognosis

• Perform gastrointestinal decontamination (activated charcoal, gastric lavage) as clinically appropriate.
• Provide supportive care to stabilize cardiac rhythm and manage gastrointestinal symptoms.
• Monitor vital signs and cardiac function closely for 24 to 48 hours post-exposure.

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Professional Toxicology

Scientific NameAsclepias syriaca L.; Asclepias cornuti Decne.

AliasesButterfly flower、Silkweed、Silky swallow-wort、Virginia silkweed

Toxicity Grade

HumansLow

CatsLow

DogsLow

HorsesSevere

Target Organs

HeartGastrointestinal tractSkinEyes

Mechanism of Action

• Cardioactive cardenolides disrupt sodium-potassium ATPase pumps in cardiac cells, leading to abnormal heart rhythm and potential failure.

• Steroid glycosides irritate the gastrointestinal tract lining, causing abdominal pain, vomiting, and diarrhea.

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Birds: Severely toxic (+++); ingestion can cause rapid, unexpected death

Cattle: Fatal if ingested, especially when alternative forage sources are limited

Sheep: Fatal if ingested, even in relatively small quantities

Confusion Risk

The following plants look similar and may be confused:

Other milkweed species Other Asclepias spp.

All Asclepias species share very similar visual traits, including milky sap and clustered umbrella-shaped flowers, and most contain similar toxic cardenolide compounds, so all should be treated as potentially toxic.

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Related Toxic Plants

Oleander

Nerium oleander

Severe, fatal to humans and all animals if ingested even in small quantities

Hemp dogbane

Apocynum cannabinum

High, toxic to livestock and humans, causes cardiac and gastrointestinal failure

Common periwinkle

Vinca minor

Low to moderate, causes gastrointestinal distress and neurological symptoms if ingested

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Data Sources

1. CliniTox (Universität Zürich)

This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.