Sugar alcohols are neither sugars nor alcohols, but they have that name because they are derived from sugars and have a chemical structure that looks like a cross between sugar and alcohol. These are sweet substances that are also low in calories, so they've become very common in everyday foods for humans. Unfortunately, one of those sugar alcohols is toxic to dogs, and that's also created some confusion about what other sugar alcohols are bad for pets.
Known: Xylitol and Dogs
Xylitol's effects on dogs -- a rapid drop in blood sugar that brings on vomiting, weakness, seizures, and death -- is now, finally, becoming more well known. After incidents with peanut butter containing xylitol, the word has finally begun to spread that dogs should never be given any foods containing xylitol, even in small amounts. If your dog has eaten something containing xylitol anyway, call your vet immediately.
Unknown: Xylitol and Cats
Cats, though, seem to be less affected by xylitol and other sugar alcohols. Cats don't typically go after sweet foods anyway; if your kitty just tried to swipe a human-food treat from you, it was more likely due to either just wanting what you had, or to another attractive feature of the food. The FDA notes that it's not known for sure if xylitol is truly not toxic to cats, but so far, there hasn't been a widespread problem for cats like there has been for dogs.
Possible: Some Better News
Xylitol appears to be the big worry when it comes to pets ingesting sugar alcohols. Other sugar alcohols and non-sugar sweeteners may not be so bad. Overall, the effects are still under investigation, though in the case of erythritol, research has long shown that this sugar alcohol is not nearly as worrisome as is xylitol. However, be cautious about what you give your pets anyway, simply because you want to feed your pets the best possible diet to begin with.
And while aspartame isn't a sugar alcohol, for those who have seen the internet meme about a dog keeling over from aspartame ingestion, Vetstreet notes that the substance in question was more likely xylitol -- if the story is true at all.
If your pet ingests something you don't want it to have, or if you find that your favorite human-food-as-pet-treat has added xylitol to its ingredients, contact your veterinarian and bring your pet in for a checkup. It is possible to save pets who have eaten foods that are bad for them.