According to the US Federal Food and Drug Administration (FDA) Center for Veterinary Medicine (CVM), the toxin, which does not threaten dogs in the same way, has not been identified; but the genus Lilium and the genus Hemerocallis produce a chemical that is present in all parts of the plant. The toxin is water soluble and causes renal tubular epithelial cells (TECs) to die. TECs are a kidney-resident population that responds and contributes to pathological processes in acute and chronic kidney disease: they mediate tubulointerstitial immune cell responses through the production of pro-inflammatory cytokines/chemokines and via interactions with the cat’s total immune mechanisms. Feline kidney damage is pathologically characterized by chronic tubulointerstitial inflammation and fibrotic scarring.

Human medicines:

Simple, over-the-counter medicines such as pain-relieving NSAIDS (Non-steroidal anti-inflammatory medications, such as ibuprofen or naproxen) can cause gastric/stomach ulcerations and quickly lead to acute kidney failure and death. A single Paracetamol/acetaminophen (Tylenol®) tablet can be fatal to a cat, as it results in damage to red blood cells: limiting their ability to carry oxygen. Untreated, it can cause severe anemia (low red blood cell count), difficulty breathing, a facial swelling, liver failure and death. Beta-blockers and cardiac medications used to treat hypertension (high blood pressure) can swiftly depress feline respiratory and cardiovascular function (severe hypo-tension): already health-compromised cats are particularly sensitive.

Cats may be playfully attracted to pills, and even like the smell in the coating of certain drugs or antidepressants (e.g., Venlafaxine/Effexor®), which initially displays as vomiting and, in more serious instances, serotonin syndrome: a dangerous condition that raises provokes central nervous system (CNS) function, elevating temperature, heart rate, blood pressure, and leading to seizures. Anti-anxiety medications, including those used to encourage weight loss, benzodiazepines (anti-convulsants/muscle relaxants or sleep aids), and amphetamines for treating ADD/ADHD act a stimulant: the affected cat may exhibit toxicosis as hyperactivity or sedation: both potentially contributing to rapid heart failure.

Antihistamines and cold remedies similarly act as a stimulant causing elevated heart rates, blood pressure, body temperature and seizures (abnormal activity in the brain), and death. Even vitamins—particularly Vitamin D derivatives — can cause life-threatening spikes in blood calcium levels in cats that can lead to kidney failure.

Yard and House plants

Azaleas and rhododendrons. These pretty flowering plants contain toxins that may result in vomiting, diarrhea, coma, leading to death. The bulbs of tulips and daffodils may cause serious stomach problems, convulsions, and heart damage. Eating just a few seeds of the Sago palm may be enough to cause vomiting, seizures, and liver failure. Also concerning: amaryllis, cyclamen, foxglove, holly, ivy, lilacs, mistletoe, and poinsettia.

See the list, below.

Grapes and Raisins

Even a small amount of grapes or raisins can rapidly develop to kidney failure. Repeated vomiting and hyperactivity are early signs; progressing to lethargy, diarrhea, reduced appetite, abdominal pain, decreased urination and abdominal pain.

Alcohol

Beverages that contain alcohol can cause vomiting, diarrhea, tremors, disorientation, trouble breathing, coma, and even death.

Raw Dough

The yeast in raw dough quickly produces alcohol and carbon dioxide. Even a small amount can expand and lead to a distended stomach and severe bloating that may require surgery to resolve.

Chocolate and Caffeinated Drinks

Chocolate contains substances called methylxanthines, which can cause vomiting and diarrhea, high body temperature, muscle tremors, abnormal heart rhythm, abdominal discomfort, increased thirst, and seizures.

Onions and Garlic

Onions, garlic, shallots, and scallions can cause damage to your cat’s red blood cells and lead to anemia. Poisoning is especially likely through concentrated forms such as onion soup mix or garlic powder. Cats with symptoms of lethargy, weakness, reduced appetite, pale gums, and orange to dark red urine should be taken to the vet immediately.

From the Department of Animal Science,
Cornell University and MSD veterinary journal:

common Flowering plants:

common Ferns:

• Asparagus Fern

• Emerald Feather

• Lace Fern

• Plumosa Fern

ASPCA List of Toxic and non-toxic Plants (with photos): click here

Pet Poison Control Centers:

Pet Poison Helpline: 855-764-7661

ASPCA Animal Poison Control Center: 888-426-4435

[1] This is why so many cats quickly died after being fed melamine-adulterated cat foods; see: Marion Nestle, Pet Food Politics - The Chihuahua in the Coal Mine (2010).

[2] True lilies (genus Lilium) grow from true bulbs. Some other common plants, may have the term “lily” in their common name (Peace, Peruvian and Calla lily) grow from tubers, not bulbs. These plants instead, contain insoluble calcium oxalate crystals, while less severe, cause irritation from physical irritation of the crystals which are immediate, such as: oral pain, hypersalivation, vomiting or diarrheal also, swelling of the oral cavity (esophagus), pharynx and tongue may occur as a result.

[3] See: K. Fitzgerald, Lily toxicity in the cat, (available: NIH, National Library of Medicine): also: D. Chaplain, Overview of the Immune Response, (available: NIH, National Library of Medicine).

[5] Daylilies, which are in the genus Hemerocallis, are likewise toxic to cats and can cause acute renal (kidney) failure and acute pancreatitis.

[6] While Lily of the Valley (Convallaria majalis) are not renally toxic, they contain cardenolides and are potently cardiotoxic. They possess cardiac glycosides, potent organic compounds that act on the cellular sodium-potassium ATPase pump, provoking cardiac arrhythmias, decreased carbon monoxide ejection, weak pulse, hyperkalemia (elevated potassium levels that affect central nervous system function), low blood pressure (hypotension), which can lead to seizures or coma; and possibly death. Treatment is largely symptomatic and supportive.