Toxic plants

Is St. John’s Wort Toxic To Cats? 

by Clair Chesterman
Is St. John's Wort Toxic to Cats

The toxic component found in St. John’s Wort plant is called hypericin.  Hypericin is a chemical created with the primary objective of repelling herbivores who may mistake the plant for food and cats are no exception. 

Hypericin is a natural hormone inhibitor that causes strange behavior and lack of balance in cats. It has the capacity to bind with cells once taken into the body (through digestion or skin contact). When hypericin is exposed to visible light, it initiates a chemical reaction that alters the charge of its electrons, harming or killing the host cell and generating burn-like symptoms.

Most horticulturists regard the plant as a nuisance owing to the difficulty of removing it from an area where it has taken root, as well as the toxicity of its tissues, which endangers both people and animals.

What Is St. John’s Wort?

St. John’s Wort with a cat in the background

St. John’s wort is a perennial herbaceous plant with large, creeping rhizomes. Its reddish stems are tall and branching in the top half, and it can reach a height of one meter. Near the base, the stems are woody and may seem jointed due to leaf scars. Branches are often grouped around a depressed base. It has slender and oblong leaves that are opposite and stalkless. The leaves of St. John’s Wort are yellow-green in color, with scattered transparent spots of glandular tissue, and are carried on the branches to subtend the shorter branchlets.

St. John’s Wort is widely found in Eurasia, particularly in temperate regions. However, because of its quick growth and toxicity, it is classified as an invasive weed in other continents such as the Americas, South Africa, and Australia. It has been used in folk medicine over centuries, and is still commercially farmed nowadays. It is known to be used to treat depression and anxiety.

Clinical Signs of St. John’s Wort Poisoning in Cats

St. John’s Wort and cats

St. John’s wort toxicity can be quite severe for cats. The following symptoms may appear in your cats after getting exposed to St. John’s Wort plant.

  • Photosensitivity
  • Blistering
  • Open sores 
  • Loss of Coordination
  • Weakness
  • Oral Irritation
  • Drooling
  • Behavioral Change
  • Agitation 
  • Depression

First Aid and Treatment of St. John’s Wort Poisoning in Cats

Cat looks at St. John’s Wort

The goal of therapy is to prevent the cat from absorbing more hypericin and exacerbating the symptoms. To that end, the vet may provide either hydrogen peroxide to induce vomiting or activated charcoal to absorb any chemicals that remain in the stomach. It’s also conceivable that the doctor would inject fluids into the cat’s body to stimulate urinating, which will help cleanse the cat’s system of toxins.

Recovery from St. John’s Wort Poisoning in Cats

Most cats will recover quickly when therapy is finished, usually within a few days. Those cats that have been seriously burnt by sunlight may, however, require some follow-up visits to ensure their wounds heal correctly. When the cat returns home from the vet, he or she should be placed in a shady area and given time to let the toxin’s effects to wear off.

Prevention of St. John’s Wort Poisoning in Cats

Keeping your cat indoors will lessen the possibility of encountering St. John’s Wort that may be growing near your house. Utilizing cat cages, playpens and other mental stimulating toys will help in keeping them indoors.

If you love plants but have cats at home, check out these lists:

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