Watercress Toxic?

Updated 2026-03-06| 3 min read| 1,200 found this helpful

Nasturtium officinale (watercress) is confirmed toxic to cats, dogs, and horses per ASPCA data

Its core toxic components are unspecified gastrointestinal irritants

Ingestion typically leads to mild, self-resolving vomiting and diarrhea in affected animals

FAQ

Is Watercress toxic to Humans?

No specific human toxicity data available; mild temporary gastrointestinal discomfort may occur if consumed in excessive raw quantities (Low)

Is Watercress toxic to Cats?

Mild vomiting, diarrhea, occasional abdominal discomfort (Low)

Is Watercress toxic to Dogs?

Mild vomiting, diarrhea, reduced appetite in rare cases (Low)

Is Watercress toxic to Horses?

Mild gastrointestinal discomfort, diarrhea, excess salivation (Low)

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Toxicity Details

Humans

Low

No specific human toxicity data available; mild temporary gastrointestinal discomfort may occur if consumed in excessive raw quantities

Cats

Low

Mild vomiting, diarrhea, occasional abdominal discomfort

Dogs

Low

Mild vomiting, diarrhea, reduced appetite in rare cases

Horses

Low

Mild gastrointestinal discomfort, diarrhea, excess salivation

Toxicity Snapshot

Toxic PartsAll fresh, raw plant parts (leaves, stems) contain irritant compounds

Exposure RoutePrimary exposure route is ingestion; dermal exposure does not typically cause adverse effects

Toxic CompoundsGastrointestinal irritant compounds (unspecified brassica-derived secondary metabolites)

First Aid & Prevention

First 30 Minutes

• Remove any remaining watercress pieces from the affected animal's mouth immediately
• Offer small amounts of fresh drinking water to dilute ingested irritants
• Monitor the animal closely for 2 hours post-ingestion for signs of gastrointestinal upset

Contact Vet Immediately

• Vomiting persists for longer than 2 hours or is severe
• Diarrhea contains blood, is very watery, or lasts more than 12 hours
• The animal displays lethargy, abdominal pain, or refuses to eat or drink

Prevention

• Keep cultivated watercress plants and wild growing patches out of reach of pets and grazing horses
• Never feed raw watercress as a treat to cats, dogs, or equines
• Regularly clear wild watercress from pastures used for horse grazing

Treatment & Prognosis

• Supportive care is the primary treatment, including fluid administration to prevent dehydration from vomiting/diarrhea
• Gastroprotectant medications may be prescribed by a vet to reduce gastrointestinal lining inflammation
• Most affected animals make a full recovery within 24 to 48 hours with appropriate care

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Professional Toxicology

Scientific NameNasturtium officinale

AliasesWatercress、Brunnenkress

Toxicity Grade

HumansLow

CatsLow

DogsLow

HorsesLow

Target Organs

Gastrointestinal tract (stomach, small intestine, large intestine)

Mechanism of Action

• Ingested irritant compounds directly inflame the mucosal lining of the stomach and intestines, increasing gut motility and fluid secretion leading to vomiting and diarrhea

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: Low toxicity; ingestion of large quantities may cause mild diarrhea and reduced feed intake

Sheep: Very low toxicity; small amounts of watercress can be consumed without adverse effects in most cases

Domestic Rabbits: Low toxicity; excess feeding may lead to soft stools or transient mild diarrhea

Confusion Risk

The following plants look similar and may be confused:

Garden Nasturtium Tropaeolum majus

Commonly called 'nasturtium' in casual use, leading to name confusion; it has round, peltate leaves and belongs to the Tropaeolaceae family, unlike watercress's pinnate leaves and Brassicaceae classification

Land Cress Barbarea verna

Has a similar peppery taste and leaf shape to watercress; grows in terrestrial rather than aquatic/wetland habitats, with lower reported toxicity risk for grazing animals

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Related Toxic Plants

Black Mustard

Brassica nigra

Moderate toxicity to livestock when consumed in large quantities

Rapeseed

Brassica napus

Moderate toxicity to horses and ruminants if grazed fresh in large volumes

Wild Radish

Raphanus raphanistrum

Low to moderate toxicity, causing gastrointestinal irritation in all domestic animal species

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Data Sources

1. ASPCA Animal Poison Control

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