Cats are smaller, metabolize toxins differently from humans, and lack some of the liver enzymes we rely on to break down compounds in everyday foods. The list below isn't a "be careful" list. It's a "these will harm or kill a cat, sometimes in very small amounts" list. Read it once, then screenshot the emergency section.
The non-negotiable list
Onions, garlic, leeks, chives, shallots. All members of the allium family destroy red blood cells in cats. The damage accumulates. A small amount of onion powder in pasta sauce, eaten daily, will cause anemia. Symptoms: weakness, pale gums, brown or red urine, fast breathing. Garlic is roughly five times more potent than onion.
Chocolate. Theobromine and caffeine. Dark and baker's chocolate are worst. Even small amounts can be dangerous for a cat. Symptoms: vomiting, restlessness, rapid heart rate, seizures.
Grapes and raisins. The mechanism isn't fully understood but they cause acute kidney failure in cats and dogs. There is no known safe dose. Symptoms: vomiting within hours, lethargy, no urination.
Xylitol (sugar substitute). Found in sugar-free gum, peanut butter, toothpaste, some baked goods, and many "keto" products. Causes a sudden insulin release and liver failure. Read every label before sharing. A friend almost lost her cat to a stick of sugar-free gum that fell out of a handbag.
Alcohol and raw yeast dough. Both produce ethanol in the bloodstream. Yeast dough also expands in the stomach. Both are emergencies.
Caffeine. Coffee grounds, tea bags, energy drinks. Cats are far more sensitive than humans. Keep used grounds out of accessible bins.
Raw fish. Contains thiaminase, which destroys vitamin B1. Long-term feeding causes neurological damage. Cooked fish in small amounts is fine.
Raw eggs. Avidin in egg whites blocks biotin absorption, plus salmonella risk. Cooked eggs are fine occasionally.
Cow's milk and dairy. Most adult cats are lactose intolerant. Not toxic, but causes diarrhea. The image of a cat lapping cream is a cultural myth that ends with a stomach ache.
Bones, cooked. Splinter and can perforate the gut. Raw bones carry their own risks (bacteria, fractured teeth) but at least don't shatter.
Liver, in large amounts. A small amount is fine and nutritious. Chronic feeding causes vitamin A toxicity, which deforms bones.
Dog food. Not acutely toxic, but lacks taurine. A cat fed dog food long-term will develop heart disease.
Houseplants that poison cats
Cats chew greenery. Several common houseplants are dangerous. One is catastrophic.
- Lilies (true lilies, Lilium and Hemerocallis). Every part is toxic. Pollen on the fur, water from the vase, a single petal. Any exposure can cause acute kidney failure within 24–72 hours. There is no antidote. If a lily is anywhere in your home, remove it today.
- Tulips, hyacinths, daffodils. Bulbs are worst.
- Sago palm. Liver failure. Highly toxic.
- Azalea, rhododendron, oleander. Heart and nervous system.
- Pothos, philodendron, dieffenbachia, peace lily. Oral irritation and swelling.
- Aloe. Vomiting and diarrhea.
The ASPCA maintains a searchable plant list. Check anything new before you bring it home.
Less obvious dangers
- Avocado. Persin is mildly toxic to cats. The bigger risk is the pit.
- Macadamia nuts. Cause weakness and tremors.
- Tomato and potato leaves and stems (raw, green). Solanine.
- Salt, in large amounts. Salty snacks aren't a daily hazard but homemade play dough is. High salt content, attractive smell.
- Essential oils, especially tea tree, peppermint, eucalyptus, citrus, pine, ylang-ylang, wintergreen. Cats can't metabolize phenols. Diffusing them in a closed room is enough to cause liver damage.
- Medications. Acetaminophen (Tylenol) is fatal to cats in a single pill. Ibuprofen and aspirin are also dangerous. Never medicate a cat with anything not prescribed for that cat.
If your cat eats something on this list
Don't wait to "see how they do." With cats, the window to act is usually shorter than you'd expect.
- Remove access to the substance and any cat in the household.
- Call your vet or an animal poison control line immediately. In the US: ASPCA Animal Poison Control (888-426-4435) or Pet Poison Helpline (855-764-7661). Both charge a fee. The fee is worth it.
- Bring the packaging or a sample to the vet. Knowing the exact product and dose changes treatment.
- Don't induce vomiting unless a vet tells you to. Many household methods (salt water, hydrogen peroxide) are themselves dangerous for cats.
Most poisonings are treatable if you act in the first few hours. The mistake people regret is waiting overnight to see if the cat seems "normal." Cats hide illness. By the time symptoms are obvious, the damage is often done.