Cats, as any cat owner will tell you, are hard to discipline. No matter how much you scold your kitty for jumping onto the counter and eating your dinner they're bound to do it again.

But there's reason to be cautious: lots of common foods can be seriously harmful to your pet. Most owners don't realize that these 15 things can make your cat sick.

And if you're a dog owner, check out our companion list of things they shouldn't eat.

If your pet has eaten something dangerous, contact your vet right away or phone the Pet Poison Helpline at 855-764-7661 (there is a fee for calling).

1. Liver

A little bit of meat now and again is a tasty treat for your cat, but liver is an exception. This meat is high in Vitamin A, which can be toxic to your cat. In high doses, eating liver will even cause a variety of bone defects in your cat, including spurs, deformities and osteoporosis.

2. Flea and tick products

These days lots of owners keep both dogs and cats, and may think of applying medicines like tick repellents on both kinds of pets. This is not advisable, since these products are only safe for one type of animal each.

In fact, flea and tick products for dogs often include pyrethins or pyrethoids, which are made from a chrysanthemum flower that's toxic to cats. Make sure your pet medicines are cat-safe before using them.

3. Xylitol

Like dogs, cats cannot digest this artificial sweetener used in products like candies, sugarless gum, diet sodas and energy drinks. Be careful not to leave products like these lying around near your pet.

4. Raw Fish

Heathcliff might chow down on raw fish all the time, but it's not safe for your cat. Compounds in the raw meat can cause thiamine deficiency in your pet, which leads to convulsions and neurological problems.

Canned tuna or salmon should also be used in moderation. It's a nice treat for your cat, but eating too much can lead to mercury poisoning, just like in humans.

5. Chocolate

Like dogs, cats have trouble digesting the compound called theobromine, which gives chocolate its bitter taste. This means dark chocolate is especially harmful to cats. Even a small quantity will cause vomiting and diarrhea. In large amounts it can cause a coma or even death.

6. Raw Eggs and Meat

Cooked meat is fine for your pet, but avoid letting them snack on uncooked protein. Cats are sensitive to parasites and viruses like salmonella that lurk in these products, and they can pass them on to you.

7. Milk

Another example of classic cartoon cat food that's just not true. Cats, like dogs, are basically lactose intolerant. Leaving Kitty a saucer of milk will only cause diarrhea and other uncomfortable stomach problems.

Keep reading, because most pet owners have no clue about this next one...

8. Caffeine

In small doses a little bit of coffee won't harm your pet, but caffeine affects their system much more than ours. Too much caffeine can raise their heart rate dangerously high and impact their nervous system. Plus, lots of caffeinated drinks also contain theobromine (the toxic compound from chocolate).

That also means it's important to safely throw out caffeine products like coffee pods and tea bags once you're done with them.

9. Bones

Cat treats like rawhide bones are actually made from animal hides, which is much softer than real bones. For cats used to chewing on kibble, bones are just too tough for their teeth. Also, be aware that cooked bones - say from a roast chicken - have a nasty habit of splintering and becoming a choking hazard.

10. Alcohol

It may seem "cute" for you pet to drink out of your glass, but alcohol is not safe for cats at all. Like other chemicals, even a small dose has a big impact on your pet's body. Two teaspoons of whiskey is enough to send a 5-pound cat into a coma, and another spoonful would kill the animal.

Your cat's liver and brain simply can't cope with the effects of liquor, so don't let them have any.

11. Allium Plants

Dog owners often have no idea that flowering veggies like chives, onions and garlic are poisonous to dogs. But these plants are even more dangerous for cats. Compounds in the plants can't be metabolized by your cat's body.

That leads to red blood cell damage and conditions like anemia. Remember that there is garlic hiding in a surprising number of foods, including gravies and even baby formula.

12. Grapes and Raisins

While veterinarians still aren't sure how toxic grapes and raisins are for felines, they recommend keeping them away from your cat because they're known to be toxic for dogs.

Look out for these symptoms, which dogs are known to experience after eating grapes: vomiting, diarrhea, bad breath (a sign of mouth ulcers) and lack of urination. In severe cases eating grapes could put your pet in a coma.

13. Acetaminophen Drugs

If your cat is in pain, you need to keep them comfortable or rely on medicine from your vet, because cats cannot take human medicine. Even a single Tylenol tablet can be fatal for a large dog, and cats are even more at risk because of their small size.

14. Yeast Dough

You shouldn't worry about letting your pet nibble on bread or pastries (even though this is unhealthy). But unbaked yeast dough is another matter entirely. As the yeast "rises," gas is released which can block your pet's stomach. It sounds silly, but this obstruction can be painful and dangerous for your cat.

15. Dog Food

It's not dangerous for Kitty to nibble on Rex's kibble every once in a while, but you can't swap cat food for dog food for an extended period. These products are formulated specifically for one kind of pet, and cats who eat dog food can actually become malnourished over time.

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