Why Are Chocolate & Onions Bad for Dogs?

Keep an eye on chocolate pastries your pup may steal.
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If you have any chocolate bars, pastries or cakes around, it's best to keep them out of your pup's reach, along with stews or other foods containing onions. Both chocolate and onions contain ingredients that are toxic to our canine friends and should never be given to them for any reason. Think your pup has partaken of these toxic foods? Bring him to the vet immediately.


Chocolate contains theobromine, a chemical that is toxic to our canine companions, along with caffeine, which is also toxic and actually enhances the effects of theobromine, according to the Michigan Veterinary Specialists. These ingredients, known as methylxanthines, come from cacao seeds, which are used to make chocolate. Some types of chocolate are more toxic to your little one than others. For example, white chocolate has the lowest amount of toxic methylxanthines, while dark and baker's chocolates have the highest, according to the Association for the Prevention of Cruelty to Animals. If your pooch has chowed down on some chocolate candy, he may experience seizures, hyperactivity, vomiting, increased or abnormal heart rhythm, tremors, collapse or even death, according to the Pet Poison Helpline.


Onions are members of the Allium genus of plants, along with garlic, chives and leeks. These plants contain thiosulphate and N-propyl disulphide, two chemicals that can cause hemolytic anemia, a condition that damages your pup's red blood cells, according to the Ontario SPCA. If your pooch ingests only 0.5 percent of his body weight in onions, this could result in damage to his red blood cells and toxicity, according to an article published in the September 2009 edition of "Interdisciplinary Toxicology." This means that just a few ounces of onions—cooked, raw or dried—could be toxic to your little one. Symptoms of onion poisoning include pale gums, lethargy, vomiting, panting, increased heart rate and low blood sugar, warns the Pet Poison Helpline.

What to Do?

If you suspect that your pup has eaten foods containing either chocolate or onions (or any other Allium species), you need to contact your regular vet or an emergency vet clinic and bring him in right away for treatment. While no antidote is available for either type of poison, your vet can induce vomiting in your pooch to empty his system of these toxins. She'll also provide him with supportive care to combat his symptoms, such as vomiting, lethargy and dehydration. In severe cases of onion poisoning, she may also need to give your pup a blood transfusion to combat the red blood cell damage that has occurred in his body. Your vet will continue to check your pup's red blood cell count and provide any intravenous fluids he needs as he recovers from the poisoning.

Avoiding Trouble

The best way to avoid accidental poisoning of your pup is to keep him away from anything containing chocolate or onions. It doesn't take much to cause a dangerous situation. While it takes about an ounce of milk chocolate per pound of body weight to poison a pooch, just 1 ounce of baking chocolate or 3 ounces of chocolate chips per 9 pounds of body weight poisons your pup just as easily, according to WebMD. Keep baked goods out of reach of your hungry canine and don't give him table scraps from meals cooked with onions. Avoid using cocoa shell mulch in your garden, which your pup could also ingest and be harmed by. If you are unsure about a food, err on the side of caution and keep it away from Fido, especially during the holidays when onion-containing foods like stuffing, gravies and salads abound.