Onions are extremely toxic for cats!
Onion powder, onion salts, cooked onion and dried onion can all cause serious problems. Even a small bit of onion in broth is harmful, and cats should steer clear of it. It only takes about 5 grams of onion per kilogram of body weight for your cat to start having symptoms. Since onions can be so dangerous and every cat reacts differently, it’s very important to avoid onions altogether.
