Cats hack up plenty of things on their own, and cat owners sure don't need an increase in volume because of something simple like an avocado.  Guacamole and several other human foods can make cats sick.  

Most pet owners know that chocolate is bad for dogs and can even be lethal.  But what foods can be toxic to cats?  It turns out there are several, and if these foods don't kill your cat, they can make them ill at the very least.

It's football party season and a lot of these foods might be lined up on the buffet.  Don't let the cat get into this stuff while you're not looking.

Human Foods That Are Toxic for Cats, according to TheSprucePets.com

Avocados - Persin is found in avocados, and it's not a huge problem, but it can be mildly toxic to cats.  It can give cats an upset stomach, which might bring on vomiting and diarrhea.  The pit would be the bigger issue if they swallowed it, but that's more of a dog risk because cats have littler mouths.

Onions - Onions have N-propyl disulfide in them, and that's a substance that destroys red blood cells and causes a form of anemia called Heinz body anemia.  Yuck.

Garlic - Garlic has the same ingredient that onions have, but it's a lesser amount.  If there's a trace amount of onions or garlic in a sauce it's probably not enough to make them sick, but you definitely don't want your cat gnawing on a whole garlic clove.

Green Tomatoes and Raw Green Potatoes - The unripened versions contain a bitter, poisonous alkaloid called Glycoalkaloid Solanine, which can cause violent lower gastrointestinal symptoms.  "Violent" and "Lower GI" are two things you never want to see side-by-side.  Especially in pets, who won't know what hit them.

Chocolate - Theobromine is bad for dogs, and it's also toxic to cats. The highest concentration is in dark and unsweetened chocolate.

Grapes and Raisins - The ASPCA isn't sure why these are bad for pets, but they're studying the effects to find out more, and in the meantime, it's best to steer clear.

Oh, and milk can make them fussy too because most cats are lactose intolerant.

I've been a dog owner all my life, but cat ownership is relatively new to me and I want to be good at it.  And holy cow, it seems that cats have enough attitude without illness playing a role.

So, the moral of the story seems to be to stick to that bagged food.  And never invite a cat to a football party.  Unless there's catnip.