Cooked or raw, onions contain thiosulphate, a substance that causes your dog’s red blood cells to burst in a condition called hemolytic anemia. Symptoms include diarrhoea, vomiting, breathlessness, and lethargy; it could take two to four days for them to become noticeable. You also put your dog at risk if you give her certain foods that are made with onions, like pizza or tomato sauce, which could trigger the same reaction.

3. Any kind of chocolate

Chocolate is the worst kind of candy your dog can eat because it contains theobromine, a substance similar to caffeine. Baking and dark chocolates have the highest levels of theobromine, but milk and white chocolate are also harmful to dogs. As with caffeine, symptoms of chocolate poisoning include high blood pressure, tremors, and seizures.

4. Fat trimmings and cooked bones

Don’t scrape leftovers from your steak dinner into the dog bowl. Not only can fat trimmings lead to obesity - it doesn’t take many extra calories for small dogs to become obese - but they also contribute to pancreatitis. Severe cases can result in a blood infection and internal bleeding. Small bones, like those found in meat, are a choking hazard, and they can splinter and tear into a dog’s throat or intestines. If your dog wants a bone, make sure it’s a raw one.

5. Bacon

We’re as surprised as you are about this one. The high fat and sodium content put your dog at risk for pancreatitis, high blood pressure, obesity, and bowel cancer. But if you pet is begging for some of your breakfast, it’s safe to slip it small bits of low-fat, low-sodium bacon. This is the kind dog food manufacturers use in their products.

Written by Claire Nowak. This article first appeared in Reader’s Digest. For more of what you love from the world’s best-loved magazine, here’s our best subscription offer.