Bright, multi-coloured, fruit-flavoured slushie ice drinks sold in cinemas, parks and soft-play settings are made to appeal to children. However, in recent years there have been numerous reports of children taking ill after consuming sugar-free versions of them, which contain glycerol.
Researchers are now calling for public health advice to be revised on glycerol-containing slush ice drinks to help avoid the possibility of children becoming intoxicated by them. They recommend that either guidelines need to be based on weight, rather than age, or children under eight years old should be banned from consuming these products altogether.
But why is glycerol used in these drinks and why is it causing children to become unwell?
What is glycerol and why is it used in slushies?
Glycerol occurs naturally in several types of lipids and is an endogenous metabolite in mammals. When it is consumed, it is normally rapidly absorbed from the gastrointestinal tract and metabolised, primarily in the liver.
Government policies to reduce sugar consumption and the introduction of the ‘sugar tax’ in the UK have led to many slushies now being marketed as ‘no added sugar’ or ‘sugar free’. In these cases, sweeteners such as stevia or sucralose are added, along with glycerol (E422) to maintain a slush of ice by preventing the liquid from freezing solid.
Is glycerol safe to consume?
Glycerol is authorised as a food additive by many countries including the UK and EU and is generally thought to be safe for humans to consume. However, there have been cases of glycerol intoxication when a very large quantity of the chemical is consumed relative to body weight.
What problems has it caused?
A retrospective case review of 21 children (median age 3½ years) who were admitted to hospital found that within an hour of consuming a glycerol-containing slushie almost all (93%) became acutely unwell. Symptoms included loss of consciousness, low blood sugar, a build-up of acid in the blood, pseudohypertriglyceridaemia (an overestimation of serum triglyceride levels due to the measurement of free glycerol) and low potassium levels. One of the children had a seizure. The authors said these symptoms are all characteristic of glycerol intoxication.
All of the children recovered after treatment and most avoided slushies afterwards. Although one did drink another at the age of seven and was vomiting and drowsy within an hour. Recognising the symptoms the child’s parent gave them a glucose polymer drink – an emergency treatment used primarily for the management of genetic metabolic conditions – which helped to resolve their symptoms. As a readily available source of carbohydrates the drink ensures the body has the right level of glucose to maintain metabolism and prevent it from breaking down alternative sources of energy, body fat for example.
The surge in cases involving glycerol-containing slushies could be the result of the reduced sugar content of these drinks, which has been driven by public and parental concerns around high sugar drinks in the UK and Ireland.
Why does it affect younger children?
Glycerol intoxication is linked to body weight and is more likely to affect younger children. In 2017, the European Food Safety Agency reported that consuming 125mg per kilogram of body weight per hour was enough to increase levels of glycerol in the blood, potentially causing intoxication.
The researchers behind the 2025 case review said that the reason that this cohort of children was susceptible to glycerol intoxication was probably multifactorial – including environmental, physiological and maybe even genetic factors.
They explained that factors such as how quickly the drink was consumed, whether the child had an empty stomach prior to drinking or if they had just done high-intensity exercise could all play an important role.
More research is needed to fully understand the exact biochemistry behind glycerol intoxication in children, they said, but made some suggestions, such as delayed maturation of enzymes involved in glycerol metabolic pathway. They also pointed out that glycerol is an osmotic agent (it has been used in the past to reduce intracranial pressure during brain surgery) and therefore the low potassium levels noted in this cohort could be caused by the osmotic effect of glycerol causing a shift in potassium levels in cells in the body.
What are the safety recommendations for these drinks?
The UK Food Standards Agency (FSA) currently recommends that slushies containing glycerol should not be given to children aged four and under, and that children 10 years old or under should not consume more than one. The FSA says this is due to their potential to cause side-effects such as headaches and sickness, particularly when consumed in excess.
The FSA has also issued industry guidelines, stating that manufacturers must formulate products containing the minimum quantity of glycerol required to achieve the desired ‘slush’. There should also be a visible warning at the point of sale and free refills should not be available to children under the age of 10. The guidelines are based on a worst-case scenario of a slush ice drink containing the top level of 50,000mg/l glycerol.
The authors of the case review pointed out that although the ingredients are listed on several slush ice drink brands’ websites, there is poor transparency around glycerol concentration meaning estimating a safe dose is not straightforward.
They also added that, given the variability in weights seen across age groups, the recommendations for these drinks should be based on weight rather than age. Alternatively, they said, the recommended age threshold should be raised to eight years old to ensure the dose per weight cannot be exceeded.
Overall, they said that, because these drinks have no nutritional benefit, recommendations needed to be weighted towards safety.
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