Xylitol is mostly safe, especially if taken in the amounts found in food. The FDA has approved it as a food additive or sweetener.
If you take large amounts of xylitol, such as 30 to 40 grams, you may have diarrhea or gas.
There’s not enough information to confirm xylitol's safety in pregnant and breastfeeding women, so they shouldn’t use it for medicinal purposes. Some animal studies have shown tumor growth from high doses of xylitol over long periods, but more research is needed.