Young children may be better off avoiding sugar-free slushees, according to new research.

British and Irish scientists reviewed the medical notes of 21 children who became acutely unwell shortly after drinking a slushee containing glycerol.

Glycerol, also known as glycerin, is used in sugar-free slushees to keep the ice from fully freezing.

It is widely used in Ireland and the UK, where sugar taxes were imposed in 2018 and 2019 respectively.

Of the cases studied, 20 occurred after 2018, with just one outlier in 2009. The children were aged from two to nearly seven.

The researchers’ findings, published in the journal Archives of Disease in Childhood, showed that in each case the child became acutely unwell with a cluster of symptoms soon after drinking a slush ice drink, which the researchers refer to as glycerol intoxication syndrome.

The features included reduced consciousness, a sudden sharp drop in blood sugar (hypoglycaemia), and a build-up of acid in the blood (metabolic acidosis).

Such symptoms, when they occur together, can indicate poisoning or inherited metabolic disorders, prompting further investigations.

How quickly they became ill was known for 15 of the children, and for 14 of those, it was within an hour.

Likewise, in 16 of the 17 cases where state of consciousness was noted, it was “significantly and suddenly reduced”, with one child even having a seizure.

Twenty of the children had hypoglycaemia, but in 13 of them it was severe.

Other common symptoms included metabolic acidosis (16 of 17 children), low levels of potassium (12 of 16 children) and falsely high blood fat levels (eight out of nine children).

All the children recovered quickly after initial resuscitation and stabilisation of their blood glucose. They were discharged with advice to avoid slushees.

Twenty did so and had no further episodes of hypoglycaemia.

But one drank another slushee at the age of seven and developed symptoms within an hour, rapidly progressing to vomiting and drowsiness, the researchers found.

The parents gave the child a glucose drink, and called an ambulance. When the paramedics arrived, the child’s blood sugar was back to normal and symptoms were already resolving.

The researchers believe current recommendations in the UK and Ireland, which advise that children four and under avoid sugar-free slushees, and children aged five to 10 should not have more than one, may no longer be enough.

“There is poor transparency around slush ice drink glycerol concentration; estimating a safe dose is therefore not easy,” the researchers wrote.

“It is also likely that speed and dose of ingestion, along with other aspects, such as whether the drink is consumed alongside a meal or during a fasting state, or consumed after high-intensity exercise, may be contributing factors.”

They recommended safe drinking levels be determined by body weight, based on current advice that 125 milligrams of glycerol per kilogram of body weight was the lowest dose associated with negative health effects.

“Alternatively, the recommended age threshold may need to be higher (8 years), to ensure the dose per weight would not be exceeded, given normal population variation in weight,” the researchers wrote.

Sugar-free and no-added sugar slushees are available in Australia, as are the sugared versions.