Flax (Linseed) Toxic?

Updated 2026-03-06| 4 min read| 1,420 found this helpful

Contains cyanogenic glycosides linamarin and lotaustralin that release toxic hydrogen cyanide when activated by the enzyme linamarase

Young green flax shoots have the highest cyanogenic compound content, reaching up to 5% of their dry weight

Cooking flax seeds for at least 10 minutes destroys linamarase, preventing hydrogen cyanide release and associated poisoning risk

FAQ

Is Flax (Linseed) toxic to Humans?

Unsteadiness, vomiting, rapid breathing, tremors, twitching, seizures, slow heart rate, coma, respiratory arrest, potentially fatal within seconds in severe cases (Severe)

Is Flax (Linseed) toxic to Cats?

No explicit confirmed poisoning cases documented; expected symptoms align with cyanide poisoning: difficulty breathing, tremors, seizures, sudden collapse (Moderate)

Is Flax (Linseed) toxic to Dogs?

No explicit confirmed poisoning cases documented; expected symptoms align with cyanide poisoning: difficulty breathing, tremors, seizures, sudden collapse (Moderate)

Is Flax (Linseed) toxic to Horses?

Confirmed poisoning cases reported; symptoms include unsteadiness, rapid breathing, tremors, seizures, slow heart rate, respiratory arrest, rapid death (Severe)

Not sure which plant? Snap a photo to ID in 1 secondGet App

Toxicity Details

Humans

Severe

Unsteadiness, vomiting, rapid breathing, tremors, twitching, seizures, slow heart rate, coma, respiratory arrest, potentially fatal within seconds in severe cases

Cats

Moderate

No explicit confirmed poisoning cases documented; expected symptoms align with cyanide poisoning: difficulty breathing, tremors, seizures, sudden collapse

Dogs

Moderate

No explicit confirmed poisoning cases documented; expected symptoms align with cyanide poisoning: difficulty breathing, tremors, seizures, sudden collapse

Horses

Severe

Confirmed poisoning cases reported; symptoms include unsteadiness, rapid breathing, tremors, seizures, slow heart rate, respiratory arrest, rapid death

Toxicity Snapshot

Toxic PartsSeeds (seed coat, 0.5% cyanide content), young seedlings; cyanide content decreases during extended storage

Exposure RouteIngestion of raw seeds, young seedlings, or improperly processed flax products

Toxic CompoundsLinamarin; Lotaustralin; Linamarase; Linatin (vitamin B6 antagonist)

First Aid & Prevention

First 30 Minutes

• Immediately move the exposed individual/pet away from flax plant material
• Administer 95% oxygen + 5% carbon dioxide ventilation if respiratory distress is observed
• If conscious and ingestion occurred within 1 hour, induce vomiting only if advised by a medical professional/vet

Contact Vet Immediately

• If any symptoms of poisoning (vomiting, tremors, rapid breathing, seizures) appear after flax ingestion
• If large amounts of raw flax seeds or seedlings are ingested, even if no symptoms are immediately present

Prevention

• Cook flax seeds for a minimum of 10 minutes before human consumption to eliminate cyanide activation risk
• Heat-treat flax oil cake before using it as animal feed to deactivate toxic enzymes
• Keep raw flax seeds and seedlings out of reach of children, pets, and grazing livestock

Treatment & Prognosis

• Intravenous administration of 1% sodium nitrite solution at 20-25 mg/kg body weight
• Follow with intravenous 25% sodium thiosulfate solution at 0.5-1.25 g/kg body weight
• Repeat half the dose of both medications if symptoms do not resolve within 15-20 minutes
• Provide continuous supportive respiratory care as needed

Emergency? Open PlantFun for real-time AI guidanceGet App

Professional Toxicology

Scientific NameLinum usitatissimum L.

AliasesCultivated flax、Common flax

Toxicity Grade

HumansSevere

CatsModerate

DogsModerate

HorsesSevere

Target Organs

Central nervous systemRespiratory systemCardiovascular system

Mechanism of Action

• Cyanogenic glycosides linamarin and lotaustralin are broken down by linamarase to release hydrogen cyanide, which blocks cellular oxygen use

• Linamarase enzyme activity is dependent on the plant's pH level and water content

• Linatin acts as a vitamin B6 antagonist, interfering with normal B6-dependent metabolic processes

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Sheep (Lambs): Confirmed poisoning cases reported; ruminants are more sensitive to flax toxicity than monogastric animals

Cattle (Calves): Confirmed poisoning cases reported; hydrogen cyanide can be excreted in cow milk after exposure to toxic flax doses

General Ruminants: Higher sensitivity to flax toxicity than single-stomach animals, as rumen pH conditions favor linamarase enzyme activity

Confusion Risk

The following plants look similar and may be confused:

Perennial Flax Linum perenne

Visually nearly identical to cultivated flax, with matching blue flower structure; also contains cyanogenic glycosides and carries equivalent severe toxicity risk

Fescue Seedlings Festuca spp.

Young flax seedlings may be mistaken for young fescue grass shoots in pastures; flax seedlings have drastically higher cyanide content than fescue

Use PlantFun to scan and avoid misidentificationGet App

Related Toxic Plants

Perennial Flax

Linum perenne

Severe

Yellow Flax

Linum flavum

Moderate

Narbonne Flax

Linum narbonense

High

Download PlantFun App

Identify, grow and care for plants effectively!

Instant Plant ID

Take a photo to quickly identify plants.

Smart Care Reminders

Generate watering and care schedules.

Toxicity & Disease Diagnosis

Identify toxic plants and pests with treatment advice.

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.