Avocados

Avocados contain a toxin called persin, which is entirely acceptable for humans but extremely toxic to dogs. Because it is present in avocado fruit, pits, leaves, and bark, you should avoid giving your dog any part of the plant.

If a dog consumes them, fluid may build up in the dog's lungs and chest. This can make breathing difficult, resulting in oxygen deprivation and possibly death. Fluid can also build up in the heart, pancreas, and belly, leading to additional deadly consequences. A dog may also ingest an avocado pit, which can cause choking or an obstruction in the digestive tract.