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Is Water Flag toxic to cats?

YES (TOXIC)
Unfortunately, Water Flag is toxic and potentially harmful to cats. We recommend you keep your feline friends away from this plant. See the table below for more information.
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Additional Names:Iris, Snake Lily, Flag
Scientific Name:Iris species
Family:Iridaceae
Toxic Principles:Pentacylic terpenoids (zeorin, missourin and missouriensin)
Clinical Signs:Salivation, vomiting, drooling,lethargy, diarrhea. Highest concentration in rhizomes.
If you think your cat may have ingested a poisonous substance, call 888 426 4435 or your local vet
Detailed Write-up
Author:
Alec
Last Updated:
7/13/25

Is Water Flag Toxic to Cats?

Cats are known for their curious and playful nature, and as pet owners, we want to ensure their safety and well-being. One concern that has arisen in recent years is the toxicity of water flag to cats. Water flag, also known as sweet flag, is a plant commonly found in wetland areas in North America and Europe. It has been used for medicinal purposes for centuries, but its potential toxic effects on cats are a cause for concern.

What is Water Flag?

Water flag, scientifically known as Acorus calamus, is a perennial plant that is commonly found in wetland areas. The plant has long, narrow leaves and a rhizome, or underground stem, which is commonly used for medicinal purposes. Water flag has been used in traditional medicine for centuries for a variety of purposes, including as a sedative, digestive aid, and anti-inflammatory agent.

What Are the Risks to Cats?

While water flag has been used for medicinal purposes for centuries, its toxic effects on cats have only recently been studied. According to the ASPCA, water flag is toxic to cats and can cause a range of symptoms, including vomiting, diarrhea, excessive drooling, seizures, and even death.

How Does Water Flag Affect Cats?

The active ingredient in water flag is asarone, which is a known carcinogen and neurotoxin. Asarone has been shown to cause liver damage and cancer in laboratory animals, and its effects on cats are similar. When ingested, water flag can cause severe gastrointestinal distress, such as vomiting and diarrhea. In addition, asarone can affect the central nervous system and cause seizures or tremors.

The toxic effects of water flag on cats can vary depending on the amount ingested and the size and age of the cat. In some cases, the symptoms may be mild and self-limiting, while in others they can be severe and life-threatening.

How Can You Protect Your Cat from Water Flag?

If you live in an area where water flag is common, it is important to take steps to protect your cat from exposure. This may include keeping your cat indoors or supervised when outside, and avoiding areas where water flag is known to grow. If you have water flag growing on your property, it is important to remove it or take steps to prevent your cat from accessing it.

If you suspect your cat has ingested water flag, it is important to seek immediate veterinary care. Your veterinarian may recommend inducing vomiting or other treatments to try to remove the toxin from your cat's system.

Conclusion

Water flag is a plant that is commonly found in wetland areas in North America and Europe. While it has been used for medicinal purposes for centuries, its potential toxic effects on cats are a cause for concern. The active ingredient in water flag, asarone, is a known carcinogen and neurotoxin that can cause severe gastrointestinal distress, seizures, and even death in cats. If you live in an area where water flag is common, it is important to take steps to protect your cat from exposure to this plant.

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