Contrary to the belief that cats are tough, they are in fact quite delicate partly because their livers simply do not process food and supplements they way ours do. With cats, when it doubt, leave it out. Hope the following caveats and cautions regarding herbs, essential oils, alcohol, and preservatives help fellow cat lovers.

Aside from the obvious dangers such as drugs acetaminophen, ibuprofen, and metacam, which can be deadly, one should also approach aspirin with extreme care. Please refer to veterinary drug sites for more details on what's safe for cats. That's not my bailiwick, so in this article as with others on my website, I steer clear of drug discussions.

As for non-drug items, please do not assume just because something is "natural" or has been used by humans for centuries, it's automatically safe for cats. That is simply not true. The list of no-nos for cats is a very long one.

One of the most dangerous is alcohol which can damage the liver and pancreas as well as cause Heniz body anemia in cats. Alcohol is quite commonly used as a preservative in medicines e.g. liquid antibiotics such as Clindamycin, injectable cyanocobalamin (B12), and in herbal as well as homeopathic tinctures. If the medicine/herb/homeopathic remedy is critical to the cat's health, then one has no choice but to weigh that benefit against associated risk. In such situations, if at all possible, look for pill/tablet/capsule in lieu of the drug or herb or remedy.

Other forms of alcohol are more easily avoided e.g. propylene glycol and ethylene glycol to which cats are even more sensitive than other animals. The former can destroy cat red blood cells and cause a very serious condition called "Heinz Body Anemia", and the latter as seen often in antifreeze poisoning can cause death from renal failure.

Cats are apparently even more vulnerable to developing heinz-body anemia than dogs, so it's best to avoid onions, chives, and garlic. Onion powder has been removed from baby food but it is a hidden ingredient in most commercial meat broths/stocks.

Please look at the well-fed section of the site for what a good commercial cat food should and should not contain. What also bears mentioning as that it is also important to avoid colorings, flavorings, fillers, and carcinogenic preservatives such as BHT, BHA, and ethoxyquin.

Herbs:

With cats, it is best to play it safe and with the exception of a few herbs, assume that most are either unsafe or at best used short-term, and all this only after a great deal of research. In other words, all traditional contraindications for humans apply to cats, and then some.

The few herbs that have a longer history of "safe" use are (safe is in quotes because no herb is totally safe, we have to weigh pluses and minuses):

Safe Longer-term:

  • Marshmallow Root and Slippery Elm Bark -- for nausea, vomiting, diarrhea, and constipation. Great for IBD cats to help rebuild
  • intestinal mucosa as well as for cats with CRF. Give at least 30-60 minutes prior to feeding to avoid nutrient absorption concerns.
  • Stinging Nettles -- for sneezing/hay fever and inhalant as well as contact allergy symptoms
  • Dandelion Leaf -- for cats with Congestive Heart Failure (CHF)
  • Aloe vera juice/gel (inner leaf/fillet only and without additives such as sodium benzoate and potassium sorbate as listed toward the end of this article) -- to help intestinal villi and heal the digestive tract.
  • Catnip –- appetite and mood stimulant
  • Turmeric or curcumin –- anti-inflammatory, emmanagogue/blood-moving for conditions such as cancer, and heart benefits.

Safe Short-term for medicinal purposes:

  • Raspberry leaf –- for queens, if needed
  • Arjuna –- a cardiotonic and beta-blocker
  • Andrographis Paniculata –- for sinus/URI problems
  • Astragalus –- immune booster, also helpful for thyroid and kidney conditions
  • Blackberry Leaf -- diarrhea
  • Boswellia Serrata-- arthritis
  • Cayenne –- arthritis (some formulations can cause stomach pain)
  • Cinnamon (water-soluble extract only), and not Cassia -– can lower blood glucose levels
  • Cranberry –- there isn't much reason to use this herb for cats with FLUTD. A better option is D-Mannose for a few days.
  • Dandelion leaf -– a diuretic containing some potassium for pulmonary edema and pleural effusion
  • Echinacea –- at the first signs of a cold
  • Fennel –- digestive upset including gas and bloating
  • Ginger -- nausea, and to increase stomach motility
  • Ginkgo Biloba -– blood-thinner good for circulatory problems
  • Ginseng – American and Siberian -– immune system; colds; physical and mental stimulation
  • Goldenseal -- antibacterial, particularly good for topical use
  • Hawthorne berries -- cardiotonic beta-blocker
  • Parsley – diuretic, however it can cause potassium loss so dandelion leaf is a better choice
  • Milk Thistle – liver problems
  • Peppermint Leaf – nausea and indigestion
  • St. John's Wort - depression/mood
  • Valerian – appetite stimulation and can be helpful for high-strung cats (though beware it can in some cases have the opposite effect)

Herbs that should never be given to cats internally:

  • Herbs containing salicin -- White Willow Bark, Feverfew, and Meadowsweet; cats have trouble metabolizing these causing "salicylate intoxication" and bleeding. With salicylate build-up that a cat's kidneys have trouble excreting, the typical presentation is symptoms of kidney failure with severe metabolic acidosis and breathing trouble. Cats much like humans with this condition have a high fatality rate. 
  • Alfalfa -- an ingredient in it - canavanine - can lead to abnormal blood cell counts and spleen enlargement as well as interfere with arginine uptake in the body. Arginine (abundant in meat) is critical for cats, and inadequate amounts of arginine can cause serious problems. See article titled "Why does the cat require a high protein diet?" by Rogers QR & Morris JG (1980) Journal of Nutrition 109, 718–723 for details on the deleterious effects of inadequate L-arginine in kitten diets. Last but not least, Alfalfa contains coumarin derivatives that can inhibit blood clotting. There is no reason to use this herb, none.
  • Garlic -- causes heinz body anemia
  • Mistletoe -- detrimental effect to the heart
  • Pennyroyal -- can be fatal to cats, and even in very diluted amounts can cause irreversible liver, lung, and brain damage. Check for this herb as one of the ingredients in those ubiquitous "flea collars"
  • Strong bitters in "worming" formulas such as Rue, Feverfew, and Wormwood which can cause kidney and liver damage.
  • Comfrey -- can cause liver damage (okay to use PA-free brands e.g. Herb Pharm's for external use on a strictly short-term basis)
  • Chapparal -- can cause kidney and liver problems
  • Lobelia -- can cause nausea and vomiting even in small doses

Herbs that can be okay but only if used with extra caution:

  • Juniper Berries -- should not be used long-term because it irritates the kidneys/urinary tract.
  • Uva Ursi -- has a strong astringent action, and should not be used long-term because it irritates the kidneys/urinary tract. Uva Ursi should only be used with alkaline urine. Even though we do not know for sure if cranberry acidifies the urine, do not use Uva Ursi together with cranberry.
  • Horsetail -- long-term use can elevate blood pressure
  • Licorice -- can lead to water retention and raise blood pressure. Best not to use on a long-term basis.
  • Ginkgo -- Do not use with allopathic heart medication/blood thinners
  • Hawthorne Berry -- Do not use with allopathic heart medication/blood thinners
  • Red Clover (one of the constituents in Essiac Tea formula) -- Contains coumarins which could affect bleeding problems in cats. Should not to be taken with allopathic blood thinning drugs
  • Goldenseal, Barberry, and Oregon Grape Root -- Strong astringent action; can kill off beneficial bacteria, so best for short-term use only.

Essential Oils

Essential oils (EOs) from any plant should never be used on or near cats because EOs can burn their skin and cat livers are unable to process the terpenes in EOs. Please read this article on Aromatherapy by certified aromatherapist Kristen Leigh Bell for more details.

Alcohol

Unlike humans, cats have not evolved consuming anything that contains naturally occurring alcohol. On my list, we have seen cats develop liver and pancreatitis problems when administered anything containing alcohol Cry And that's stuff we can see, so who knows what sort of damage occurs over time..

Most homeopathic tincture preparations and flower essences contain at least 20% alcohol with LM tinctures containing up to 90-95% alcohol. This means it's not a good idea to use them neat other than topically. If using internally, a reasonable dilution rate might be no more than 2 drops per 15ml/0.5oz dropper bottle of water. If a weaker dilution works, e.g. 1 drop, try that first. Even better would be to use pills/pellets instead.

Herbs can contain anywhere from 10% to 70% alcohol in certain tincture preparations, so using these without making sure the alcohol has been removed as much as possible is a bad idea. Freshly ground seeds e.g. Milk Thistle, Milky Oats, and capsules containing freeze-dried powdered herbs are usually the best bet with cats for this reason. For information on how to remove alcohol from a herbal tincture, stay tuned, an article will be added soon.

Other Cautions

Beware of potassium sorbate and sodium benzoate as they are both unsafe for cats. Alas, both of these are common preservative in aloe vera juice and gel formulations. There is only one brand available without sodium benzoate in all their products- George's Aloe Vera Juice. Another brand -- Lily of the Desert while good, uses potassium sorbate for most of their product line. Thankfully, there is one safe Lily of the Desert version -- their pure preservative-free aloe vera inner fillet (not whole leaf) juice. Read labels carefully because the logo and other packaging information is very similar to their less "pure" items.

Cats are extremely sensitive to Alpha Lipoic Acid (ALA). In the study referenced below, it was found that ALA is ten times more toxic to cats than to other species. Thay also found hypoglycemia and "hepatocellular toxicity". It was suggested that the maximum safe dosage to be less than 30mg per kg of body weight.

Bottom line -- research every single thing you give your cat, and if you can't do so, err on the side of not using a product rather than risk liver damage, heinz body anemia, bleeding, kidney failure, and a host of other serious problems as many of them can lead to death.

If you'd like help navigating cat safety issues or anything else cat, click here for a consult.

References

Christopher MM, Perman V, Eaton JW., Contribution of propylene glycol-induced Heinz body formation to anemia in cats, J Am Vet Med Assoc. 1989 Apr 15;194(8):1045-56.

Bedford PG and EG Clarke, Experimental benzoic acid poisoning in the cat,Vet Rec., Vol. 90, Issue 3, 53-58, January 15, 1972

Benzoic Acid and Sodium Benzoate, International programme on chemical safety: concise international chemical assessment document no. 26
Hill, A.S., Werner, J.A., Rogers, Q.R., O'Neill, S.L. & Christopher, M.M. Lipoic acid is10 times more toxic in cats than reported in humans, dogs or rats. J. Anim. Physiol. Anim. Nutr.(Berl)., 2004, 88(3-4), 150-156

Erika G. Loftin and Lee V. Herold, Therapy and outcome of suspected alpha lipoic acid toxicity in two dogs, Journal of Veterinary Emergency and Critical CareVolume 19, Issue 5, pages 501–506, October 2009

Keun-Woo Lee, Osamu Yamato, Motoshi Tajima, Minako Kuraoka, Shogo Omae, and Yoshimitsu Maede, Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs. Am J Vet Res. 2000 Nov;61(11):1446-50.

Osamu Yamato, Ei Kasai, Taro Katsura, Shinichi Takahashi, Takuji Shiota, Motoshi Tajima, Masahiro Yamasaki, and Yoshimitsu Maede, Heinz Body Hemolytic Anemia With Eccentrocytosis From Ingestion of Chinese Chive (Allium
tuberosum) and Garlic (Allium sativum) in a Dog, Journal of the American Animal Hospital Association 2005, 41:68-73