Chocolate This may not be shocking to many animal lovers, but pets do not appreciate the joys of chocolate quite as much as humans, probably because it kills them. Chocolate contains two closely related compounds: theobromine and caffeine. At high doses, these effects can cause muscular overstimulation, potentially leading to abnormal heart rhythms, muscle tremors, diarrhea, restlessness, and heart failure. As a matter of fact, humans are able to break down theobromine much more quickly and efficiently than what a dog’s metabolism is capable of. Onions What makes people cry and pets die? If you answered onions, you’re surprisingly correct. Onions are very poisonous to cats and dogs due to compounds known as N-propyl disulfide and sodium n-propylthiosulfate. When ingested, these chemicals reduce the formation of an important antioxidant called glutathione, which ultimately causes toxic hydrogen peroxide levels to rise up. Symptoms to look out for include weakness, vomiting, diarrhea, pale gums, discolored urine, and overactive saliva production. Macadamia Nuts Macadamia nuts are highly valued by snack lovers for their high contents of minerals, antioxidants, and more. Dogs can also get a few bonus side effects if they consume these delicious snacks: vomiting, weakness or mild paralysis, hyperthermia, and muscle tremors. The exact cause of macadamia nut toxicity in canines is unknown. Grapes And Raisins Grapes don’t exactly emit an aura of danger, but these small snacks have very large consequences when ingested by a dog. The exact mechanism of toxicity is still a mystery, but it is known that consumption can cause dogs to develop acute kidney failure. Symptoms commonly include vomiting and diarrhea, weakness, loss of appetite, lack of urine production, and others. Unlike macadamia nuts, this type of poisoning is very severe and often fatal. Sweeteners If your dog is feeling bummed about not being able to eat chocolate anymore, here’s some exciting news: It’s no longer allowed to eat candy as well! Xylitol is a sugar alcohol commonly added to sweets such as chewing gum and candy as a low-calorie sugar substitute. When ingested by dogs, however, xylitol triggers a large release of insulin, a compound that induces cells to take up sugar from the blood. This sudden surge of insulin flowing into cells can result in a sudden decrease in the dog’s blood glucose, resulting in a condition known as hypoglycemia. Lilies Pet owners know that cats love to chew on plants for no reason in particular. However, this seemingly benign habit could quickly turn into a medical emergency if lilies are brought into the mix. Various species of lilies are popular household decorations and extremely poisonous to cats. Consumption of any part of the plant will cause symptoms such as vomiting, depression, dehydration, and abnormal urination patterns. Avocado Despite being a beloved staple at parties worldwide in the form of guacamole, avocados seem to be poisonous to nearly everything except humans, one of the few mammals capable of eating this delicious fruit. Avocado contains a natural antifungal substance known as persin, which has been demonstrated to cause heart muscle and mammary gland necrosis in various species. While cats and dogs haven’t been known to exhibit well-documented side effects, other potential pets such as horses, rabbits, mice, sheep, and other domesticated animals have exhibited harmful symptoms after the repeated consumption of avocado. Bread Dough Getting bloated and dying from alcohol poisoning seems like the kind of death only a human would manage to pull off, but pets can experience this same fate if they consume uncooked bread dough made with yeast. In bread dough containing fermenting yeast, the release of carbon dioxide is what makes bread rise. The expanding dough could potentially cause a gastric blockage and make the animal’s stomach distended and bloated. Furthermore, the ethanol byproduct released by fermentation will be absorbed into the bloodstream, causing alcohol poisoning, which can quickly prove to be lethal if the animal isn’t rushed to the doctor. Sago Palms The sago palm resembles a miniature tropical palm tree and would be a seemingly innocent plant to give your backyard a little tropical taste. Ingestion of this plant by pets can be extremely lethal. The plant contains numerous toxins with varying effects, the most prominent being a compound called cycasin. Upon consumption, cycasin is broken down into a compound called methylazoxymethanol. This causes liver failure by damaging liver cells and interfering with the liver’s ability to produce glucose. Fireflies Fireflies contain self-defense poisons called lucibufagins that, when ingested, have proven to be highly lethal to various potential pet reptiles, including chameleons and lizards such as the bearded dragon. Amphibians like frogs are also at risk.After eating the insects, lizards often retch or vomit and experience a dark change in skin color. Before you chuckle at the irony of a reptile turning black after eating a bright, glowing insect, know that this is no laughing matter. At this point, death often follows after about two hours.