At first, although there were rumblings about the toxicity of alfalfa on such websites as the ASPCA, there was little substance to sustain the comments I was reading. Eventually, with a little work, here is some of what surfaced:
Alfalfa may, because of the presence of eugenol in the herb, inhibit certain liver microsomal hydroxylating systems. This produces toxic effects from drugs normally metabolized by those systems.
Among the several phenolic compounds assayed for their phytotoxicity on root and shoot growth of alfalfa, coumarin and trans-cinnamic acid at 60 +/- 10 micrograms mL-1 were the most inhibitory. Mixtures of five or more phenolic acids were more phytotoxic than their respective individual components except in the case of trans-cinnamic acid and coumarin.
Alfalfa = Coumarin (acts as an anticoagulant)
Warfarin toxicity can occur as a result of ingestion of pharmaceutic Coumadin or after exposure to the rodenticide superwarfarins. It may be from intentional or unintentional overdose or as a consequence of drug interactions.
The story of the anticoagulant-cum–rat poison begins with an agricultural strategy of the early 1900s, the introduction of sweet clovers in the North American prairies. In 1924 ranchers in Alberta, Canada, observed that cattle feeding on moldy sweet clover were dying from a hemorrhagic disorder; the active agent was found to be dihydroxycoumarin (coumarin itself is shown below). This molecule was synthesized within a year and quickly found use as an anticoagulant. Meanwhile warfarin, the derivative of coumarin, was developed by University of Wisconsin biochemists Mark A. Stahmann and Karl P. Link, and used as a rodenticide. It took 10 years for it to enter clinical practice as a blood-thinner.
Aloe is a member of the lily family, and there a number of varieties, some more of a problem than others. There are more than 500 species of aloe growing in a variety of climates worldwide and only three or four of those are reported to have medicinal properties. Sabaea is particularly bad with compounds such as coniine, which is capable of producing both depressant and excitatory effects on the spinal cord of the cat. It has been compared with curare, and strychnine. This type of information is important if you are growing aloe plants in your house, and possibly applying aloe externally for skin irritations and other folk remedies, as there needs to be specific processing done on a safe variety in order for the resulting product to be "food grade" for your cat, as your cat licks his or her fur.
Depending upon the variety of aloe, and the processing done, to prepare it, there are a number of ways it is used as a human medicine, such as as a laxative and skin salve, a cancer treatment, a glucose control mechanism, and immune system enhancer, however, if you have any plans to use this plant on your cat, or internally, I would definitely look into the variety source and chemicals used for processing further, based upon the chemicals this plant contains that are harmful. Keep in mind the term "Food Grade" when searching for a suitable source. There are also warnings out there that aloe compounds can interfere with regular medications, causing them to be less effective, at best.
Here is an ingredient you wouldn't expect to see on this list, however, if your pet is prone to struvite crystals, be aware that chlorophyll contains magnesium as the core of its molecule, and magnesium is said to contribute to struvite crystals in cats.
Essential oils of rosemary have demonstrated antimicrobial, hyperglycemic, and insulin-inhibiting properties.98,99 The next site states: "These data suggest that the volatile oil of R. officinalis has hyperglycemic and insulin release inhibitory effects in the rabbit."
A postprandial elevation in plasma glucose levels 30 min after administration of maltose or sucrose plus the distilled extract was significantly suppressed compared with glucose levels in mice that did not receive the distilled extract.
Garlic and Onion
In particular Onion, more than garlic, is a blood thinner, and doesn't go well with home testing where you may need your cat's blood to clot within a reasonable time. In fact, my own experience with this was when Hamlet had been sunning himself on the deck, next to the chives, on a day when I was doing a curve. It wasn't until the second time that I smelled freshly chopped chives and realized that the copious amount of blood that came with the small prick of the lancet was a result of Hamlet cheating with the chives. They contain Sodium 2-Propenyl Thiosulfate that oxidizes, (rusts), erythrocytes, also known as red blood cells which is where the term anemia evolves in the well known condition, Hemolytic anemia. Propylene Glycol, sometimes found in pet foods, causes the same effect.
Yucca schidigera extract is included in pet foods to reduce faecal aroma, as an aesthetically pleasing ingredient for humans, rather than a nutritional additive for felines. What pet owners are not told is that the results of the study mentioning the motivation, above, also states the following: " Blood urea increased significantly in YSE-treated cats, possibly due to the saponins of YSE affecting gut wall permeability. This finding contrasts with previously published reports of a reduction in blood urea on the addition of sarsaponin (from YSE) to rat diets and of YSE products to poultry and cattle diets." In other words, while yucca is not showing harmful side effects in studies on other animals, and chickens, cats, with their more sensitive GIT DOES show an effect in lab results for cats.As stated in the British Journal of Nutrition, Volume 88, Number 6, December 2002, pp. 587-605(19), "These structurally diverse compounds have also been observed to kill protozoans and molluscs, to be antioxidants, to impair the digestion of protein and the uptake of vitamins and minerals in the gut, to cause hypoglycaemia, and to act as anti fungal and antiviral agents. These compounds can thus affect animals in a host of different ways both positive and negative."Yucca is also a member of the Liliaceae family. The University of Pennsylvania suggests that members of the lily family have long term effects, "consistent with acute renal failure".