Why it's dangerous
Oleander contains cardiac glycosides that interfere with the electrolyte balance within the heart muscle, specifically affecting the sodium-potassium pump.
Toxic compound: Oleandrin
Good to know
All parts of the plant are toxic, including the water in which the plant has been placed. It is related to other cardiac glycoside plants like Foxglove and Lily of the Valley.
Sources
This page is informational and is not veterinary advice. If your pet has been exposed to something risky, contact your vet or an animal poison control line right away.