While it’s certainly tempting to feed your pet human foods, it’s often not a good idea. Some human foods are okay in moderation, but for the most part, your pet will do best eating a diet scientifically designed for them. Human foods are often too high in fat, sugar and calories, contributing to obesity, digestive upsets, allergic symptoms, tooth decay, nutritional deficiencies and even outright toxicity.

Here are some human foods pets should avoid:

1. Onions and garlic

The compound in a cut onion that makes humans shed tears is the same one that’s poisonous to both dogs and cats. Garlic contains about five times as much of the toxin as onions do, but it takes only a small amount, as little as one gram per pound of animal, to produce serious illness in either species. The toxic compound causes the red blood cells to break down, causing a severe, life-threatening anemia.

2. Raw Eggs and raw meat and bones

There is great controversy regarding the feeding of a raw food diet to both dogs and cats. The main concern here is bacterial contamination by salmonella and other pathogens. Although both dogs and cats have stronger stomach acid than humans do, this may not be enough to prevent illness from bacterially contaminated foods. The truth is, a raw egg or two occasionally isn’t likely to cause your pet any harm, but bones should be avoided because they can cause tooth breakage, oral injury, choking and possible perforations.

3. Chocolate

While not usually fatal to dogs unless consumed in very large amounts, this sweet treat contains a compound called theobromine that can make a dog or cat very sick. Cats are more prone to this kind of toxin. As little as a quarter ounce of the baking variety or a half ounce of bittersweet or dark chocolate can kill a cat. The baker’s and dark types are more dangerous for both species than the milk type because they contain far higher amounts of the theobromine-containing cocoa. Theobromine is a stimulant, causing increased heart rate, seizures, muscle tremors, vomiting and possible death.

4. Caffeine

There aren’t many foods attractive to pets that naturally contain this compound, but dogs who root through the trash and consume coffee grounds or used tea leaves may ingest a risky amount of caffeine. While cats are unlikely to drink cola or coffee, dogs may lap them up, especially if the coffee has cooled and contains copious amounts of cream and sugar. Dogs may also accidentally swallow diet pills containing large amounts of this substance, which is a dangerous stimulant capable of causing abnormal heart rhythm and possible death for both dogs and cats.

5. Grapes and raisins

Grape and raisin toxicosis can cause fatal kidney damage in both dogs and cats. This includes grape juice and wine, which dogs may readily lap up. Dogs may also consume raisin-containing trail mix or come upon an open box of the sweet morsels. Cats are more likely to play with a grape or raisin than to eat it, but if they do, it’s an emergency. Think before offering your dog or cat a piece of fruitcake or a bit of cookie because both may contain raisin residue. No amount is safe, and worse, scientists aren’t even sure exactly what the problem is. If you know or suspect your pet has ingested even one grape or raisin, treat it as a medical emergency and call the vet immediately.