Dozens of common foods can make dogs sick, ranging from mildly upsetting their stomach to causing organ failure within hours. The most dangerous ones include chocolate, grapes and raisins, xylitol (a sugar substitute), onions and garlic, macadamia nuts, and raw yeast dough. Some of these are surprising because they’re perfectly healthy for humans.
Chocolate, Coffee, and Caffeine
Chocolate is one of the most well-known dangers, but the risk depends heavily on the type. All chocolate contains compounds called methylxanthines that dogs process much more slowly than humans do. These compounds speed up the heart, overstimulate the nervous system, and at high enough doses can cause seizures or death. The lethal dose of theobromine, the primary methylxanthine in chocolate, is 100 to 500 mg per kilogram of a dog’s body weight.
What matters most is how dark the chocolate is. Baking chocolate and cocoa powder have the highest concentrations, making even a small amount dangerous for a small dog. Dark chocolate is next. Milk chocolate is less concentrated but still risky in larger quantities. White chocolate has the lowest levels and is unlikely to cause methylxanthine poisoning, though its high fat content can still trigger digestive problems. Coffee and caffeine carry the same type of risk. Symptoms include vomiting, diarrhea, rapid breathing, excessive thirst, hyperactivity, abnormal heart rhythm, and tremors.
Grapes and Raisins
Grapes and raisins can cause acute kidney failure in dogs. The toxic compound has recently been identified as tartaric acid, which is naturally present in grapes and becomes more concentrated when grapes are dried into raisins. This means raisins are more dangerous per gram than fresh grapes.
What makes grapes especially tricky is that the tartaric acid content varies between grape varieties and even between individual batches. Some dogs eat a grape or two and show no symptoms, while others develop kidney failure from a similar amount. Because there’s no way to predict which dogs will react severely, veterinarians treat every grape or raisin ingestion as a potential emergency. Vomiting, lethargy, and decreased urination are the early warning signs.
Xylitol and Sugar Substitutes
Xylitol is a sugar alcohol used in sugar-free gum, candy, peanut butter, baked goods, and some toothpastes. It’s extremely dangerous for dogs. Even a small amount triggers the pancreas to release a massive surge of insulin, three to seven times the amount that regular sugar would cause. This flood of insulin crashes blood sugar levels within 30 to 60 minutes, causing weakness, vomiting, loss of coordination, and seizures. Larger amounts can cause liver failure, which can be fatal.
Not all sugar substitutes carry the same risk. Erythritol and monk fruit sweetener are not toxic to dogs. Stevia, aspartame, sucralose, and saccharin aren’t toxic either, though they can cause digestive upset like diarrhea if a dog eats a significant amount. The critical thing is reading labels: if a product says “sugar-free,” check whether xylitol (sometimes listed as “birch sugar”) is an ingredient before letting it anywhere near your dog.
Onions, Garlic, and Related Plants
Onions, garlic, leeks, chives, and shallots all belong to the allium family, and all of them can damage a dog’s red blood cells. The compounds in these plants cause oxidative damage that essentially destroys red blood cells from the inside, leading to anemia. Cats are more susceptible, but dogs are clearly at risk too, especially with repeated exposure or a large single dose.
Cooking doesn’t eliminate the danger. Cooked onions, onion powder, garlic powder, and foods seasoned heavily with these ingredients all carry the same risk. Signs of allium poisoning may not appear for several days, making it easy to miss the connection. Watch for pale gums, lethargy, weakness, reddish or brown urine, and rapid breathing.
Macadamia Nuts
Macadamia nuts cause a distinctive but usually temporary syndrome in dogs. Within 12 hours of eating them, dogs typically develop weakness (especially in the hind legs), vomiting, tremors, elevated body temperature, and a wobbly, uncoordinated walk. The exact toxin responsible hasn’t been identified, but the pattern is consistent and well-documented.
The good news is that macadamia nut poisoning is rarely fatal. In experimental studies, dogs given macadamia nuts at 20 grams per kilogram of body weight developed symptoms within 12 hours and recovered completely without treatment within 48 hours. That said, the combination of macadamia nuts and chocolate, which shows up in cookies and candy, can be significantly more dangerous than either one alone.
Raw Yeast Dough
Raw bread dough poses two separate threats. First, the warm environment inside a dog’s stomach is ideal for yeast to keep rising. The dough expands, causing painful bloating that can progress to a life-threatening stomach twist (gastric dilation-volvulus). Second, the yeast fermentation process produces ethanol as a byproduct, effectively brewing alcohol inside the dog’s stomach. Dogs with bread dough toxicosis have shown vomiting, loss of coordination, blindness, dangerously low body temperature, and an inability to stand, all classic signs of alcohol poisoning.
Cooked Bones
Bones are the most commonly reported esophageal foreign body in dogs, accounting for 30% to 80% of cases in veterinary studies. Cooking makes bones brittle, so they’re more likely to splinter into sharp fragments that can scratch or puncture the esophagus, stomach, or intestines. Bones that get stuck in the esophagus are especially problematic: the longer they stay lodged, the more erosion they cause to the tissue. Bones trapped in the lower esophagus are roughly 13 times more likely to cause tissue damage than those caught higher up.
Chicken, turkey, and pork bones are the worst offenders because they’re small, hollow, and splinter easily when cooked. If you want to give your dog a bone, raw bones are generally considered safer because they’re more flexible, but they still carry some risk of cracking teeth or causing blockages.
Fatty Foods and Dairy
Rich, greasy foods like bacon, ham, fried scraps, and butter can trigger pancreatitis, a painful inflammation of the pancreas. This doesn’t always happen the first time a dog eats something fatty, but repeated exposure or one large fatty meal (like Thanksgiving leftovers) is a common cause. Symptoms include severe vomiting, abdominal pain, diarrhea, and loss of appetite. Nuts like almonds, pecans, and walnuts are particularly risky because of their high fat content.
Dairy is a milder issue. Dogs produce very little lactase, the enzyme needed to break down the sugar in milk. Cheese, ice cream, and milk can cause gas, bloating, and diarrhea, though small amounts are tolerated by many dogs without problems.
Avocado
Avocado’s reputation as a dog toxin is more nuanced than it first appears. The fruit does contain a compound called persin, but the concentration varies dramatically by part. The peel contains about 720 micrograms per gram, the flesh about 110, and the pit about 99. In a study feeding dogs a diet containing processed avocado meal, no persin was detectable and no dogs showed signs of toxicity. Heat processing appears to break persin down entirely.
The bigger practical risk from avocados is the pit, which is the perfect size to lodge in a dog’s esophagus or intestine and cause a blockage. The high fat content of avocado flesh can also contribute to stomach upset or pancreatitis in dogs prone to it.
Alcohol
Alcohol is rapidly absorbed after ingestion, and dogs are far more sensitive to it than humans are. Beer, wine, liquor, and even alcohol-containing foods like rum cake can cause vomiting, diarrhea, difficulty breathing, tremors, and in severe cases, coma or death. Dogs are small enough that even modest amounts can produce dangerous blood alcohol levels. Keep in mind that raw yeast dough and fermented fruits can produce alcohol in the gut even if a dog hasn’t directly consumed a drink.
What to Do If Your Dog Eats Something Toxic
Speed matters. For xylitol, symptoms can begin within 30 minutes. For chocolate, it may take a few hours. For grapes, kidney damage may not show up for a day or two. Regardless of the food, contact a veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 as soon as possible. Have the packaging available if you can, and try to estimate how much your dog ate and when. The size of your dog relative to the amount ingested is the single most important factor in how serious the situation is.