There are several vegetables and fruits that dogs should avoid.
Most people enjoy spoiling their dogs and giving them treats, including giving them "people food," as it is called. There is nothing wrong with this if you remember dogs are not small humans. Canine bodies are different from human bodies, some human foods can sicken dogs and even kill them. Check with your dog's veterinarian if you are in doubt. Several types of fruits and vegetables are harmful to dogs and should never be eaten. Additionally, any food that causes your dog to have diarrhea should be off limits.
Avocados, Tomatoes and Potatoes
Avocados contain persin which is toxic to dogs. Persin is found in the fruit as well as the seed, leaves and bark of avocados. Keep all parts of the avocado from your dog's reach, as well as any foods that contain avocado. Tomatoes and potatoes are part of the toxic "nightshade" family of plants containing glycoalkaloids and are poisonous to dogs. Green tomatoes are especially poisonous. Dogs can eat cooked potatoes, but no raw potatoes or potatoes with sprouts or green on them.
Plums, Peaches, Apples & Persimmons
These fruits are safe for dogs as long as they only eat the fruit. Peach pits are toxic, containing cyanide, as are apple, cherry and plum seeds. Additionally, dogs often end up sick because of an obstruction by a peach or plum pit. Dispose of the pits in a manner that protects your dog. A dog that ingests a peach pit which obstructs its digestive tract can die before the cause of the illness is found.
Grapes & Raisins
Although many people have often fed grapes as treats to their dogs, this has now been found to sometimes have deadly results. The ASPCA Poison Control Center states that, "Although the toxic substance within grapes and raisins is unknown, these fruits can cause kidney failure." Even if you have given grapes to a dog in the past without incident, don't assume it won't cause severe illness the next time.
Nuts
Macadamia nuts, as well as foods containing them, are toxic to dogs. In some dogs, as few as six nuts can cause illness. Walnuts are also poisonous to dogs. Other kinds of nuts are safe, but don't confuse walnuts or macadamias with safe nuts. Be careful of baked goods that may have hidden macadamias or walnuts in them, as well as nuts and crumbs that can easily fall on the floor and be missed. The dog won't miss those tidbits; most dogs have a bit of a sweet tooth as well as a habit of exploring the world with their mouths. The shells of walnuts are even more toxic than the nut itself. Any nut, even nontoxic varieties, can cause choking if your dog gets it caught in the throat or sucked into the windpipe, since dogs tend to eat quickly.
Onions, Garlic & Chives
These are toxic in all forms, including seasonings such as garlic powder; they can destroy the dog's red blood cells. You may notice that some pet foods and dog treats list garlic and onions as ingredients. These amounts are not enough to cause problems. But it still doesn't take much: according to WebMD, even the small amount of onion powder sometimes found in baby food can be enough to cause serious illness.
Chocolate, Sodas & Coffee
The ASPCA Poison Control Center states that these products "all contain substances called methylxanthines, which are found in cacao seeds, the fruit of the plant used to make coffee and in the nuts of an extract used in some sodas." Dogs seem to love chocolate, but resist the temptation and don't give chocolate treats. There are carob treats made for dogs, which have a chocolate taste, but are safe. Dogs should not have anything with caffeine in it, as caffeine is part of the group called methylxanthines.
Mushrooms
Some wild mushrooms are poisonous to dogs and others are safe. Even experts cannot always tell the difference just by looking, so it's safest to assume that all wild mushrooms growing in your yard or along your walking paths are poisonous. Check your yard and places you frequent with your dog, as there are numerous varieties of wild mushrooms and they grow practically anywhere.
Symptoms
Take your dog to the veterinarian immediately if you see that it has eaten a poisonous vegetable, fruit or other substance. Sometimes your dog may find and eat something without your noticing. Be aware of the kinds of symptoms that can occur, and take the dog to the vet if you notice anything unusual. Weakness, vomiting, ataxia (uncoordinated movements), extreme thirst, tremors, increase or decrease in the amount or frequency of urine, lethargy, depression or hyperactivity are only a few of the possible symptoms