Everyone knows there are certain things that you should never feed your dog. Dogs and chocolate don’t mix, because chocolate contains theobromine, a substance that can cause a rapid heart rate and central nervous stimulation, possibly leading to seizures and even death. Most people know that dogs should never eat cooked bones because they can splinter and lodge in or even lacerate a dog’s throat or digestive tract.

But there are other items that humans commonly eat and drink that can be harmful to dogs. Today’s pet foods contain so many fruits and vegetables that we might begin to assume that anything humans eat is fine for dogs as well. Dog foods today commonly include blueberries, carrots, sweet potatoes and other foods that can be found just as often on our own dinner plates. But certain food items that, although perfectly fine or even very healthy for humans, should be kept away from dogs.

Although some human foods, like carrots, are fine for dogs, others may be toxic or even fatal. Photo by Petrina Calabalic/©Dreamstime.

Chocolate is dangerous for dogs because, as mentioned, it contains theobromine, but it also contains caffeine, which can be toxic to dogs if ingested from coffee, coffee grounds, tea or tea leaves, colas, stimulant drinks and in some over-the-counter medications. Signs of caffeine overdose may include labored or rapid breathing, hyperactivity, a rapid heart rate, shaking and even seizures.

Scientists aren’t sure exactly why, but eating raisins or grapes can cause renal failure in some dogs. It seems that as few as seven raisins can lead to vomiting, diarrhea and shaking, and eventually to a shutdown of the kidneys. In the face of these symptoms, if you have any reason to suspect your dog may have had access to raisins or grapes, seek immediate attention from a veterinarian.

Believe it or not, an overdose of onions can also cause toxicity in dogs that can lead to death. Onions contain substances called thiosulfates and allyl propyl disulfides that can destroy red blood cells and lead to anemia, ultimately causing liver damage. Onions in any form – raw, cooked, dried or even onion powder – can cause problems, and even small amounts eaten regularly can lead to poisoning. Anemia, if left untreated, can easily become fatal. Signs may include listlessness, lack of interest in food, labored breathing and vomiting. Garlic and chives also contains thiosulfates. Onion toxicity can present with the same symptoms as other serious problems, such as autoimmune hemolytic anemia. It is best to keep onions and garlic away from dogs and, if your dog exhibits symptoms of toxicity, to seek veterinary attention immediately. However, garlic is sometimes used in small amounts in dog food, which is not harmful.

Avocado plants, and the avocado fruit itself, contain persin, a substance that can cause vomiting and diarrhea in dogs. Persin is found in the leaves and bark of the plants, in the seed, and in the fruit and skin.

Although the fruit of the apple itself is not toxic to dogs, apple seeds contain cyanide and may be dangerous. Likewise, the pits of peaches and plums, which may seem to a dog like an ideal treat to chew on, contain cyanide and can be toxic. The seeds of persimmons can cause small intestine inflammation in dogs.

Although we often think they’re immune from substances that might be harmful to us, dogs can pick up salmonella and E. coli from raw eggs and raw meat, just like humans can, and may suffer the same symptoms of food poisoning we do. It is best to cook eggs and meat before feeding to your dogs. Some types of raw fish, including salmon, trout, shad and sturgeon, may contain a parasite that causes “fish disease” or “salmon poisoning disease,” and can be fatal within weeks if left untreated. Signs may include vomiting, elevated temperatures and enlarged lymph nodes. These parasites can be eliminated by thoroughly cooking fish before it is fed to your dog.

Xylitol, used to sweeten candy, gum, baked goods and other foods, can cause an increase in insulin levels in dogs, which will cause the dog’s blood sugar levels to drop and can lead to liver failure. Symptoms may include vomiting, listlessness and a lack of coordination, and may lead to seizures.

Consumption of macadamia nuts in dogs has been known to lead to symptoms such as weakening of the hindquarter and/or inability to walk normally, other apparent weakness, depression, hyperthermia (or lower than normal body temperature), muscle tremors and rapid heartrate. The reason for toxicity is not known, and dogs are the only species in which signs of toxicity have been reported. It appears that as few as six nuts can make a dog ill, though ingestion is not believed to be fatal.

Alcoholic beverages – including beer, wine and liquor – can cause damage to the liver and brain of humans if drunk in large quantities, and it takes far less to do the same damage to a dog. Alcohol consumption can cause vomiting, diarrhea and coordination problems in your pet, and even in relatively small quantities can lead to difficulty breathing, central nervous system problems and even coma or death. The smaller the dog, the greater the danger.

This is by no means a comprehensive list of foods and other substances that, while frequently ingested by humans, may prove toxic for pets.Although not all dogs will necessarily react the same way to each of them, it is best to keep food and drink containing dangerous substances away from all pets. It is also important to note that some substances that can be harmful to cats, but not to dogs.

If you suspect that your dog or other pet may have ingested something harmful, call your veterinarian or check with the ASPCA Animal Poison control Center at 1-888-426-4435. You can also visit the center on the Web, where the organization provides a wealth of information about foods, plants and other products and substances that might harm your pet, and what to do if you suspect your pet may have been poisoned.