BHT, BHA, and Ethoxyquin
These are chemical preservatives which are very effective at preserving dry cat food, but are suspected to be potentially cancer-causing agents.
Meat
Don't buy product that only mention meat without clarification what kind of meat.
By Product
By-products are not necessarily low quality protein sources. In fact, they can be extremely nutritious. However, there is more variability when quality is being considered when compared to muscle meat. Cat eat their prey as a whole means they need the nutrition from bone, kidney, liver, etc as well.
Grain and Corn
Grains should be absent but, unfortunately, grains are cheap so they are included in many commercial cat foods. If grains are present, they should be minimal in amount. Cat is an obligate carnivore.
Onions, Garlic, and Chives
Onion in all forms, powdered, raw, cooked, or dehydrated can break down a cat's red blood cells, leading to anemia.
Grapes and Raisins
Grapes and raisins have often been used as treats for pets. But it's not a good idea. Although it isn't clear why, grapes and raisins can cause kidney failure in cats.
Correct me if im wrong 