Why xylitol is dangerous for dogs but not people
In humans, xylitol doesn't trigger much of an insulin response, which is exactly why it's marketed as a sugar substitute. In dogs, it does the opposite: it prompts a rapid, significant release of insulin, which can cause blood sugar to crash within 30–60 minutes of eating it.
It hides in more places than most owners expect — sugar-free gum and mints, some peanut butters, baked goods, and certain toothpastes and supplements. Checking the ingredients label on anything sweet before it goes near your dog is the simplest prevention.
Symptoms can appear within 30 minutes of ingestion and include vomiting, weakness, wobbliness and, in more serious cases, seizures — the speed of onset is exactly why this is treated as an emergency rather than something to monitor at home overnight. Keeping xylitol-containing products stored well out of reach, the same way you would medication, is the simplest ongoing precaution. Better safe than sorry, always.