Toxic foods for dogs: chocolate, xylitol, grapes and onions

Four common kitchen foods can poison a dog badly enough to kill it: chocolate, the sweetener xylitol, grapes and raisins, and onions and garlic. With all four, treatment works best before signs appear. If a dog eats any of them, call a vet or the ASPCA Animal Poison Control Center (888-426-4435) right away, with the packaging at hand, rather than waiting at home to see what happens.

Foods that can be fatal

Chocolate

Chocolate contains theobromine and caffeine, two stimulants in the methylxanthine group. Dogs clear theobromine slowly. The Merck Veterinary Manual gives its half-life in dogs as 17.5 hours, which is why a poisoned dog can stay ill for a day or more. Merck puts mild signs at about 20 mg of methylxanthines per kg of body weight, heart effects at 40 to 50 mg/kg and seizures at 60 mg/kg or more.

The darker and less sweetened the chocolate, the less of it a dog needs to eat. The table uses Merck's methylxanthine figures for a 10 kg (22 lb) dog. Real products vary, so treat these as rough guides, not safe limits.

Signs usually start 6 to 12 hours after eating. Thirst, vomiting, diarrhea, a swollen belly and restlessness come first. Larger doses bring tremors, a racing or irregular heartbeat, overheating and seizures. White chocolate carries almost no theobromine, but its fat and sugar can still cause stomach upset.

Xylitol

Xylitol is a sugar substitute found in sugar-free gum, mints, candy, some peanut butters and baked goods, and in non-food products such as toothpaste, chewable vitamins and some liquid medicines. In dogs it triggers a fast, dose-dependent release of insulin that drops blood sugar. According to Merck's xylitol entry, doses above about 100 mg/kg can cause hypoglycemia, and some dogs that eat more than 500 mg/kg develop liver failure.

Low blood sugar can show within 30 minutes as vomiting, weakness, wobbliness, lethargy, seizures or coma. When the xylitol is in something that slows absorption, such as some gums, signs can be delayed by up to 12 to 18 hours. Xylitol content varies widely between brands of gum, so there is no safe number of pieces. Check the ingredient list of anything sugar-free before a dog can reach it, and treat any exposure as an emergency. Cats are not affected in the same way; dogs are the only domestic species in which xylitol poisoning has been reported.

Grapes, raisins and currants

Grapes and dried grapes can cause acute kidney injury. For years nobody could explain why one dog ate a bunch without harm while another went into kidney failure after a few. The leading explanation is tartaric acid. A case series from the ASPCA Animal Poison Control Center's records described dogs that developed kidney injury after eating cream of tartar or tamarinds, both rich in tartaric acid, with findings that matched grape poisoning. The amount of tartaric acid differs between fruits, which may account for the unpredictable doses.

That means there is no known safe amount. Vomiting, lethargy and loss of appetite may appear first. As the kidneys fail, a dog may pass little or no urine, which is a very bad sign. Early decontamination by a vet, followed by fluids and kidney blood tests, gives the best chance. Cream of tartar and tamarind should be kept out of reach for the same reason.

Onions, garlic, leeks and chives

These plants contain sulfur compounds that damage red blood cells, leading to a type of anemia marked by Heinz bodies. The Merck entry on Allium poisoning notes that signs have followed 15 to 30 g/kg of raw onion in dogs and that garlic is three to five times more toxic than onion. Cooked, dried and powdered forms are all harmful, which makes onion powder in gravy, stock and seasoned leftovers a common source.

Signs are slow. The damage starts within a day, but a dog often looks unwell only a few days later, once enough red cells have been destroyed. Watch for weakness, pale gums, fast breathing, reluctance to exercise and red or brown urine.

Foods that need a call to the vet

Macadamia nuts

Macadamias cause weakness, vomiting, wobbliness, tremors and a raised temperature. Merck records signs after about 2.4 g of nuts per kg of body weight, starting within 12 hours and usually settling within 12 to 48 hours. The cause is not known. Most dogs recover without specific treatment, but a vet should still assess the dog, and chocolate-coated macadamias carry the chocolate risk as well.

Alcohol and raw yeast dough

Alcoholic drinks, and foods made with them, can cause vomiting, diarrhea, poor coordination, depression and breathing difficulty in dogs, according to the ASPCA's list of foods to avoid. Small dogs need very little to be affected.

Raw bread or pizza dough is a double problem. The warm stomach lets the dough keep rising, stretching the stomach painfully, and the yeast produces alcohol as it ferments. A dog that has eaten raw dough needs to be seen promptly.

Coffee, tea and caffeine products

Caffeine is a methylxanthine, like theobromine, and causes the same kind of signs: restlessness, panting, vomiting, a fast heart rate and, at high doses, tremors and seizures. A lick of spilled coffee is unlikely to matter. Coffee grounds, beans, tea bags, energy drinks and caffeine tablets are concentrated, and eating any of these warrants a call.

Cooked bones

Cooking makes bones brittle. Chicken and pork bones in particular break into sharp shards that can cut the mouth, lodge in the throat or gut, or pierce the intestine. Raw bones carry their own risks of fractured teeth, blockages and bacterial contamination. Repeated retching, a hunched stance, straining, bloody stools or refusal to eat after a dog has eaten bones need urgent attention.

Foods that usually cause milder illness

Avocado

Avocado is often listed as toxic to dogs because of persin, but the ASPCA describes persin as mainly a problem for birds, rabbits, horses, donkeys and ruminants. For dogs the bigger hazards are the large stone, which can block the gut, and the fat in the flesh, which can upset the stomach.

Salt and salty snacks

A few potato chips will do no harm. Large amounts of salt cause heavy thirst and urination, vomiting and diarrhea, and in severe cases tremors and seizures. Dogs get into trouble with whole bags of salty snacks, homemade play dough, rock salt and seawater. Fresh water should always be available.

Nutmeg

Nutmeg contains myristicin. The pinch in a slice of cake is not a concern. A dog that chews a whole nutmeg or gets into a jar of the ground spice should be discussed with a vet or poison line.

Fatty foods and pancreatitis

Bacon, sausages, fat trimmings, butter, gravy and fried food can set off pancreatitis. The Merck Veterinary Manual says dietary indiscretion is believed to be a common risk factor in dogs and reports Miniature Schnauzers as heavily overrepresented, with higher rates also in Yorkshire Terriers, Cocker Spaniels, Dachshunds and Poodles. Severe cases bring vomiting, refusal to eat, weakness, dehydration and a painful abdomen, and some are fatal. Mild cases can look like a vague off day. A dog that vomits repeatedly or stops eating after a fatty meal should see a vet the same day.

Often misunderstood

Milk and dairy

Dairy is not poisonous, but many adult dogs produce little lactase, the enzyme that digests milk sugar. Milk, ice cream and large amounts of cheese often cause gas and diarrhea as a result. Some dogs tolerate small amounts of plain yogurt or cottage cheese. Cheese is also high in fat and salt, so it works best as an occasional small training treat.

Corn cobs

Sweetcorn kernels are harmless. The cob is the problem. Dogs tend to swallow chunks whole, cob does not break down in the gut, and the pieces are the right size to stick in the small intestine. A blocked intestine often needs surgery. Vomiting, a painful belly or no stools in the day or two after a dog has eaten a cob, including one taken from the trash, need a vet visit.

Cherries, peaches, plums and apricots

The ripe flesh is fine in small amounts. The stones, stems and leaves contain compounds that release cyanide when crushed and chewed, and whole stones can also block the gut. Remove the stones and stems before sharing any of these fruits.

If a dog eats something toxic

1. Move the dog away and collect what is left. Note what was eaten, roughly how much, when, and the dog's weight. Keep the wrapper or label.
2. Call a vet or poison line before doing anything else. The dose calculation decides whether the dog needs treatment, and time matters most with xylitol and grapes.
3. Do not make the dog vomit unless a vet tells you to. Salt given to make a dog sick can itself cause salt poisoning, and vomiting is dangerous after sharp objects or caustic products, or in a dog that is already drowsy or seizing.
4. Go straight to a clinic for seizures, collapse, breathing difficulty, pale gums, or repeated vomiting.

Most of these cases start with an open trash can, a bag on the floor, or a guest sharing food. A lidded trash can, chocolate and baking supplies stored in high cupboards, and a household rule about feeding the dog from the table prevent the majority. Handbags deserve a mention, because sugar-free gum and mints are often carried in them.

Sources

1. Chocolate toxicosis in animals. Merck Veterinary Manual.
2. Xylitol toxicosis in dogs. Merck Veterinary Manual.
3. Acute kidney injury in dogs following ingestion of cream of tartar and tamarinds and the connection to tartaric acid as the proposed toxic principle in grapes and raisins. Journal of Veterinary Emergency and Critical Care, 2022.
4. Garlic and onion (Allium spp) toxicosis in animals. Merck Veterinary Manual.
5. Macadamia nut toxicosis in dogs. Merck Veterinary Manual.
6. People foods to avoid feeding your pets. ASPCA Animal Poison Control Center.
7. Pancreatitis in dogs and cats. Merck Veterinary Manual.