As a general rule, it’s best to avoid feeding your cat human food, as their digestive system is not designed to handle many of the foods we eat. Some human foods can even be toxic to cats, causing serious health problems or even death. Here are some of the most common foods that are toxic to cats:

1. Onions and Garlic: Onions and garlic contain compounds that can damage a cat’s red blood cells, leading to anemia. Even a small amount of onion or garlic can be harmful to a cat, so it’s best to avoid them altogether.
2. Chocolate: Chocolate contains a compound called theobromine, which can be toxic to cats. The darker the chocolate, the more theobromine it contains, and the more dangerous it is for cats. Symptoms of chocolate toxicity can include vomiting, diarrhea, rapid breathing, and seizures.
3. Grapes and Raisins: Grapes and raisins can cause kidney failure in cats. It’s not clear why this happens, but even a small amount can be dangerous. Symptoms can include vomiting, diarrhea, and lethargy.
4. Caffeine: Caffeine can cause restlessness, rapid breathing, heart palpitations, and muscle tremors in cats. In severe cases, it can lead to seizures and death. It’s best to keep all caffeinated products, such as coffee, tea, and soda, away from your cat.
5. Alcohol: Alcohol can cause vomiting, diarrhea, difficulty breathing, and even coma or death in cats. Even a small amount can be harmful, so it’s important to keep all alcoholic beverages out of your cat’s reach.
6. Milk and Dairy: Contrary to popular belief, cats are actually lactose intolerant, which means they can’t digest milk and other dairy products properly. Feeding your cat milk or dairy can cause diarrhea and other digestive problems.
7. Raw Meat and Fish: Raw meat and fish can contain harmful bacteria, such as Salmonella and E. coli, that can make your cat sick. They can also contain parasites that can cause serious health problems.
8. Fat Trimmings and Bones: Feeding your cat fat trimmings and bones can cause digestive problems, including vomiting and diarrhea. Bones can also splinter and cause serious internal damage to your cat’s digestive system.
9. Dog Food: While it’s not necessarily toxic, feeding your cat dog food can be harmful to their health. Dog food does not contain the right balance of nutrients that cats need, and can lead to malnutrition and other health problems.

Overall, it’s best to stick to a high-quality commercial cat food that meets all of your cat’s nutritional needs. If you want to give your cat a treat, choose something that is specifically made for cats and is free from harmful ingredients. And always be sure to keep any potentially harmful foods out of your cat’s reach.