Mother Earth Living

Pet Corner: Toxic Plants

I once read that more than 700 plants are toxic to animals. Whew! Some folks must think that almost every weed on the planet is a potential pet killer.

But, as my grandkids say, chill out. You don’t need to fret about each and every herb you use–especially when you know some commonsense safeguards. All of my pet patients have taken herbal prescriptions, and I’m very comfortable with herb safety and effectiveness.

Admittedly, some herbs can be toxic to pets–especially when used incorrect­- ly. Cats in particular are extra-sensitive because they have digestive systems that are vulnerable to substances that pose no problems for other critters. And certain herbs shouldn’t be used on any animal at specific times, such as during pregnancy or nursing.

Toxic or not?

The American Society for the Prevention of Cruelty to Animals (ASPCA) and other sources list several herbs as potentially toxic to animals, including eucalyptus, foxglove, primrose, cherry seeds and leaves, and aloe vera. But this list may not provide the whole picture. For example:

Licorice root may cause sodium retention, a danger to some heart patients. Some reports of licorice toxicity involve potent extracts once used to make candy; whole licorice is the most widely used herb in Traditional Chinese Medicine, valued for its adaptogenic and flavoring effects. Nearly all my animal patients have taken licorice root without ill effects.

Pennyroyal is supposed to repel fleas, so it’s often used in products such as flea collars. But there have been several reports of cats dying after wearing the “all natural” collars. The collars are typically made of distilled pennyroyal essence, which can be fifty times stronger than tea from the whole plant. But I’ve watched my cats in our backyard pennyroyal patch, eating the leaves and rolling with glee much as they do with their other favorite plant, catnip. I haven’t seen any adverse effects from the whole plant, but use caution with the essential oil.

St.-John’s-wort may cause “photosensitization,” a word that in itself is obviously meant to scare the bejeezus out of you. Photosensitization simply means that the animal is more sensitive to sunlight, and it happens only rarely. St.-John’s-wort has far fewer side effects than the newer “designer drugs” that have recently come on the market to help with pet behavioral problems, which can cause nausea, joint problems, fluid retention, mania, and dizziness.

Onion is the new “no no” herb. Skeptics love to point to it when they try to discredit herbal therapies. Experiments on cats show that onions, even in small amounts, cause red blood cell abnormalities. But I know several holistic veterinarians who routinely prescribe onion, and they haven’t reported any problems. What’s going on here? It could be a matter of dosage, but it also may be oxidation. Cats under the care of a holistic veterinarian would typically be taking an antioxidant supplement, making them far less susceptible to the adverse effects of onion.

Aloe has also been reported to be toxic; what appears to be behind these cases is an irritating substance in or near the skin of the leaf. Inner parts–the gel or juice–of the plant seem absolutely safe. My cats munch on the aloe plants (leaf skin and all) that we grow in our garden and indoors, and I have no fear of using the gel externally. It’s simply too good a healer to pass up.

Valerian root is one of my favorite examples of unfounded paranoia regarding herbs. Occasionally a client will say they’ve read somewhere that valerian may act as a stimulant instead of a sedative, or that it causes headaches or damages cells. Rest easy. Valerian has been tested extensively and has been safely used by millions of people for centuries.

Cell damage reports have come from experiments using an extracted constituent of valerian, a very strong form of medicine. And, its stimulating effect is exactly how it works in cats. Valerian-sensitive cats respond to it much like catnip–rolling around in playful glee–then find a quiet place to let its sedative effects take hold.

Consider form and function

Tonics are the most beneficial and least toxic herbs and can help your pet achieve balanced health. Almost daily in my practice I prescribe tonic herbs, including licorice root, milk thistle, hawthorn berries, Siberian ginseng, sarsaparilla, stinging ­nettle, and dandelion root.

By definition, tonic herbs have four characteristics that contribute to their safety. First, they balance body systems, bringing them back to normal. Second, their action is bi-directional, meaning that some active compounds will stimulate an organ system if needed, while other compounds will depress activity if the organ needs to be “quieted.” Third, tonics are generally free of side effects and cautions. Fourth, they can be taken daily in small amounts.

For an herb to act as a tonic, all of its ­biochemical substances must be present. An extract–whether a tincture, essential oil, tablet or capsule–pulls out some, but not necessarily all, of the plant’s active ­substances. What’s left behind may be a component of the plant’s ability to act bi-directionally. Extracting also concentrates compounds, increasing the chance of a bad reaction. Essential oils in particular shouldn’t be used internally; be cautious if you apply them externally because pets lick them off.

All of this is to say that the safest way to give your pet herbs is to use the whole plant (leaves, roots, flowers), sprinkled over food. Teas added to food are a close second–they’re a very mild form of extraction and often the easiest way to help your pet enjoy herbs. If you must use the herbs in medicinal fashion (as manufactured products, in high dosages, or for specific medical problems), consult a professional.

Even though whole tonic herbs are extremely safe to use, any animal may have an unusual reaction. I recommend treating your pet with tonic herbs in small amounts for short periods of time while your pet is healthy. This way you’ll be able to mon­itor any idiosyncratic reactions before a ­crisis requires that you administer herbs medicinally.

Learn the herb

There’s no shortcut to understanding how herbs can be used effectively. Have at least five good herbal reference books on your shelves, read several accounts about the herb in question and, if any of them report adverse side effects, put up the yellow caution flag and learn more about that herb.

Finally, ask the experts. For $15, the ASPCA National Animal Poison Control Center can provide its Household Plant Reference, a list of plants reported to be toxic to animals. Call (888) 426-4435.

Randy Kidd holds doctorates in veterinary medicine and veterinary and clinical pathology. After practicing traditionally for ten years, he opened Honoring the Animals, a holistic practice in Kansas City, Missouri.

Information provided in “Pet corner” is not intended to replace the advice of a qualified veterinarian.

  • Published on May 1, 1999
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