You probably know that you shouldn't feed chocolate to your dog — but maybe your dog got into your lolly stash anyway, and came out fine. Meanwhile, your vet is more concerned that you admit to feeding him raisins. Confused? Let's take a look at what the dangers really are. Illustration by Sam Woolley.
Here's the lowdown on what we know about some of the foods that are most dangerous to dogs. Before we begin, however, two things are important to understand for each food: What the food can do to your dog, and how much it takes to cause harm. These numbers are fairly well understood for some things, like chocolate, but not for others, like grapes.
What's the danger? Chocolate can cause hyperactivity and, with higher doses, heart damage, seizures and death. The dangerous parts of chocolate are the caffeine and a related chemical, theobromine. They're both in a chemical family called methylxanthines. Coffee and tea also contain methylxanthines, but your dog is more likely to pig out on chocolate than on coffee grounds.
How much is a problem? It depends on the type of chocolate. White chocolate has almost no methylxanthines, milk chocolate has some, dark chocolate has a lot and baking chocolate is the most concentrated.
Mild symptoms, like hyperactivity, appear when a dog has had about 20mg of methylxanthines per kilogram of the dog's body weight. Heart problems occur with about 40mg, seizures at 60mg and death at 100-200mg/kg.
Put this all together and you'll realise the danger depends on the size of dog, the type of chocolate and the amount eaten. A 9kg pug, for instance, would only have mild symptoms from eating a chocolate bar, but could reach a fatal dose with just 50g of baking chocolate. That's why your dog doesn't drop dead after eating a chocolate chip cookie: Even for a small dog, there just isn't that much methylxanthine in a few chips. But if your dog steals some baking chocolate, or gets into a stash of dark chocolate, their snack could easily turn deadly.
This calculator from Veterinaryclinic.com can help you figure out whether your dog ate enough to require medical attention.
Grapes and Raisins
What's the danger? Dogs can develop acute kidney failure after eating grapes, raisins or Zante currants (which are actually not currants, but tiny raisins). The dog might vomit soon after eating the raisins, but the kidney damage takes time to occur. Symptoms may take two to three days to show up.
How much is a problem? This is the tricky part. We don't know. Veterinarians have collected examples of dogs that died after eating just a handful of raisins, while other dogs have eaten a kilogram without showing any ill effects. We also don't know what the toxic component of grapes is — so it's possible some types of grapes have more of the mystery ingredient than others. Until this mystery is solved, many vets consider any amount of raisin ingestion to be an emergency.
What's the danger? It's not the gum that's the issue here — it's the sweetener. Xylitol is a sugar alcohol used as a low kilojoule sweetener in gum and some low-kilojoule foods like sugar-free pudding. When a dog eats that gum or pudding, it can cause dangerously low blood sugar within minutes to an hour afterwards. Symptoms include weakness, difficulty walking, seizures and coma.
How much is a problem? Different products have different amounts of xylitol. In some brands, just over one piece of gum can cause hypoglycemia in a 9kg dog, with only five pieces needed to cause liver failure. Many companies don't want to state how much xylitol is in their product (secret recipe and all). In the US, some companies have shared this information with the Pet Poison Helpline for use in emergencies. Here's the hotline's fact sheet on xylitol. Australians can get more information on preventing xylitol poisoning from Pet Stay Advisor. Bottom line, keep anything with xylitol or unspecified sugar alcohols away from your pet.
Onions and Garlic
What's the danger? Dogs who eat large helpings of onions or related vegetables (like garlic, shallots and leeks) can have vomiting, diarrhoea and abdominal pain. More seriously, the sulphur-containing chemicals in these foods can destroy red blood cells, leading to anaemia. In rare cases this can be deadly.
How much is a problem? It only takes 15-30g of onion per kilogram of the dog’s weight to cause detectable changes in the blood. This is equivalent to a 14kg dog eating a whole, large onion. The sulphur compounds that cause anaemia aren’t destroyed by cooking or drying, so even a bowl of leftover beef stew, if it was cooked with onions, could be harmful to your dog.
The damage can also add up over a few meals, so even if your dog seemed fine after one night eating onion-containing table scraps, several nights of the same could still be a problem. Onions and garlic are in some pet foods and treats, so it may be worth checking labels and avoiding those products if your dog eats a lot of them.
What's the danger? Macadamia nuts aren't deadly, but dogs who eat the nuts may develop hind limb weakness, vomiting and tremors. Symptoms can occur within 12 hours of eating the nuts, and generally resolve, even without treatment, within two days.
How much is a problem? The toxin in the nuts is unknown, and so far the amount it takes to cause symptoms seems to vary. Again, it may be something only present in some nuts, perhaps even something like a mould that commonly grows on macadamia nuts. The smallest dose that has caused symptoms was 0.7g of nuts per kilogram of body weight. That's just three nuts for a 9kg dog. On the other hand, some dogs have needed 62 grams per kilogram, or over 200 nuts for the same size dog.
What to Do If Your Dog Eats Something Poisonous
If you think your dog has eaten something dangerous, your first step should be to seek help or advice. Don't immediately try to make your dog throw up, or try to give them medications. Let a vet decide, because sometimes these measures can do more harm than good.
If your dog is showing signs of poisoning already, like foaming at the mouth, shaking or bloody vomit or diarrhoea, you'll want to get her to a vet as soon as possible. But if your pet seems to be acting more or less normally, take a moment to seek advice. Call your vet or one of the 24-hour hotlines.
Acting quickly can save your pet's life, or at least reduce your vet bills. It may be possible to pump the dog's stomach to remove some of the toxic food, for example, but this only works before they have fully digested it. Some of the effects of poisoning can also be reduced with prompt medical treatment, like IV fluids to protect the kidneys of a dog who ate too many raisins.
Better than treatment, of course, is prevention — so make sure that these unsafe foods are out of your pup's reach, or out of your home entirely. While you're at it, check for medications, alcohol and household chemicals, too. Your dog won't understand why those yummy looking treats are now off limits, but at least he'll be safe.