Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

The use of xylitol, a naturally occurring substance that is widely used as a sugar substitute, has increased dramatically in the last decade due to its low glycaemic index and dental plaque fighting properties. Xylitol is found in many food products, gums, sweets and OTC medications and is also available in bulk as a sugar substitute for baking.

Xylitol is safe for use in people, although like most sugar alcohols, it may have a mild laxative effect when eaten in large amounts or when first introduced to a diet. This occurs because xylitol can pull water into the intestines or it can be fermented by bacteria present in the intestines.

Xylitol is extremely toxic to dogs. Even small amounts of xylitol can cause hypoglycaemia (low blood sugar), seizures, liver failure or even death in dogs. It seems that dogs are the most sensitive to xylitol poisoning. Cats, rabbits, ferrets and horses do not appear to develop hypoglycaemia or liver failure from ingestion of xylitol.

In both humans and dogs, the blood sugar level is controlled by the release of insulin from the pancreas. Xylitol does not stimulate the release of insulin from the pancreas in humans. However, when dogs eat xylitol, the xylitol is quickly absorbed into the bloodstream, resulting in a massive release of insulin from the pancreas.

This rapid release of insulin causes a severe drop in blood sugar, within 10 to 60 minutes after eating. If untreated, hypoglycaemia can be life-threatening. The mechanism by which xylitol causes liver failure in dogs is not understood. In general, lower doses of xylitol cause hypoglycaemia, while higher doses cause liver failure.

Signs of low blood sugar may include any or all of the following: Vomiting, weakness, lack of coordination or difficulty walking or standing, weakness/sluggishness or lethargy, tremors, seizures and coma. In severe cases, the dog may develop seizures or liver failure. Dogs that develop liver failure from xylitol poisoning may or may not show signs of hypoglycaemia first.

A presumptive diagnosis of xylitol poisoning is made if you know or suspect that the dog ate something containing xylitol, and there are signs of hypoglycaemia or liver failure. Since clinical signs develop rapidly, your veterinarian will not generally wait for a confirmed diagnosis regarding the specific amount ingested before beginning treatment.

There is no antidote for xylitol poisoning, although treatment with intravenous dextrose (glucose) supplementation and liver protective drugs are beneficial. In all cases of ingestion your dog will require hospitalisation. The prognosis is good for dogs that are treated before clinical signs develop or for dogs that develop uncomplicated hypoglycaemia that is quickly reversed. If liver failure develops, the prognosis is generally guarded and patients may need prolonged treatment.

There has been a proven episode of a mass poisoning by xylitol of about 30 sunbirds in the Cape. The nectar which had been made and set out in the feeder was made with xylitol. The birds and a sample of the nectar in the feeder were submitted to the Johannesburg Zoo for further evaluation and the final diagnosis was xylitol poisoning. So, please be very careful if you are making up nectar for birds that you do not use xylitol-containing products.

Generally, flowers offer one of three nectar sugars as rewards for pollination: Glucose, fructose and sucrose. Within the protea plants, on which sunbirds are highly dependent, only two genera of 16 produce small amounts of xylose (1 – 39%). The other 14 produce none.