Xylitol is a sugar substitute and is a more recently recognized toxin in dogs. Xylitol is often used in baked goods, desserts, gum, candy, toothpaste and other oral care products.
Ingestion of xylitol can cause diarrhea and excess gas production but the more severe signs are hypoglycemia (low blood sugar) and hepatic (liver) disease. Signs of hypoglycemia include weakness, ataxia, and seizures. These can be observed as soon as 30-60 minutes after ingestion but may be delayed several hours. Hepatic failure may be observed within 9-72 hours of ingestion and signs can include weakness, depression, vomiting, lethargy, abdominal pain, hemorrhage, and seizures.
As little as 0.15 grams/kilogram xylitol can cause hypoglycemia. This is equal to 2 grams in a 30 lb dog or 0.7 grams in a 10 lb dog. Ingestions of 0.5 gram/kg or more can put dogs at risk for hepatic disease. This is equal to 7 grams in a 30 lb dog or 2.25 grams for a 10 lb dog.
So what does this mean in terms of gum-a common source of exposure? This can be difficult as many gums only list the total sugar alcohol content on the label. It can be estimated that if xylitol is the primary (first sugar alcohol listed) then 1-2 grams per piece can be present. If xylitol is not the first sugar ingredient then estimate that there is 0.3 g xylitol per piece of gum. So approximately one-two pieces of gum could be toxic in a 10 lb dog. For baked goods, 1 cup of xylitol weighs about 190 grams.
Treatment of the asymptomatic patient includes inducing vomiting and possibly oral sugar supplementation. For symptomatic patients IV fluids with dextrose and hourly blood sugar monitoring are needed as well as hepatic protectants and antioxidants along with appropriate serum chemistry monitoring. Prognosis is good in animals who only develop hypoglycemia but guarded in those with full blown liver disease.