Both grapes and raisins can be toxic. Some dogs can eat them with, seemingly, no ill effects. However, some dogs become ill after ingesting only a few grapes or raisins. The first symptom is vomiting, followed by acute kidney failure, from which many dogs do not recover. As of yet, the toxin is unknown, nor do we know why some dogs become sick and others eat grapes or raisins without a problem.

Bread dough containing yeast can ferment in a dog's stomach, releasing large quantities of alcohol. Small dogs are more susceptible to this toxicity. Dogs who eat this may become very ill from alcohol poisoning.

Dogs can ingest as few as six macadamia nuts and become paralyzed. Dogs with macadamia poisoning can appear anxious and have difficulty moving their rear legs. Luckily, the paralysis is temporary and clears up within a few days.

Salmon and trout can be infected with a parasite called Nanophyetus salmincola, a type of trematode worm. These worms themselves can be infected with a type of bacteria known as Neorickettsia helminthoeca. The bacteria only infects canids; other animals show no symptoms from eating it. When dogs eat raw fish infected with this bacteria, they can show symptoms including weakness, vomiting, loss of appetite, swollen glands, and fever. Ninety percent of untreated dogs will die. Cooking kills the worm and the bacteria.

Onions and garlic contain a chemical called thiosulfate. When ingested either in large quantities or in small quantities over a long period of time, they can cause an anemia called Heinz Body Anemia. This is reversible if you stop feeding the onions or garlic.

This toxicity called Xylitol usually occurs when dogs eat large amounts of sugar-free candy or gum. In humans, Xylitol does not cause a drop in blood sugar; in dogs it does. This can lead to weakness, staggering, and other symptoms of hypoglycemia. There is also some evidence that some dogs may develop liver failure after ingesting Xylitol.

Cooked chicken bones are much more dangerous than uncooked bones. They are much more brittle than raw bones and can splinter into sharp shards.

In dogs, pancreatitis often results from eating a very high-fat meal. While dogs that are used to eating a high-fat diet, like sled dogs, can eat pure fat with no problems, dogs that are not used to such foods often cannot. When such a dog eats a high-fat meal, its pancreas overproduces enzymes, to the extent that they actually begin to "digest" the pancreas and inflame it. Common culprits are turkey skin and ham fat. Symptoms include vomiting and stomach pain. This is a medical emergency, and such dogs must be treated by a vet. Some breeds, like miniature schnauzers, are genetically predisposed to pancreatitis.

A common food by-product used in gardens called Cocoa Bean Mulch, has been found to cause vomiting, tremors and fast heartbeat when dogs eat it. Cocoa bean shells contain the same toxic theobromine that chocolate does, and are poisonous to dogs for the same reason. The mulch has an attractive chocolate smell that is irresistible to many dogs.

Despite common misconceptions, poinsettias are only mildly toxic, and most dogs who eat them will experience no symptoms at all. Some dogs will drool or vomit after eating them. Holly causes intense nausea, vomiting and diarrhea. Mistletoe causes vomiting, diarrhea, neurological problems and heart failure.