At very high levels of exposure, typically when several servings of these products are consumed by a child in a short space of time, glycerol can cause shock, very low blood sugar levels and loss of consciousness.  

The FSA advises that children aged 7 to 10 should have no more than one 350ml ‘slushie' drink per day – roughly the size of a fizzy drink can.

Retailers have been asked to support this advice by not offering free refills to children aged under 10.

In addition, the manufacturers of slush ice drink concentrates have also been reminded to use only the minimum amount of glycerol necessary to achieve the frozen effect. 

The guidance and the public awareness campaign have been timed to coincide with the seasonal spike in slush ice drink sales at children's indoor play areas, leisure facilities and outdoor events. 

FSA chief scientific advisor, Professor Robin May, said: ‘As we head into the summer holidays, we want parents to be aware of the potential risks associated with slush ice drinks containing glycerol.

‘While these drinks may seem harmless and side effects are generally mild, they can, especially when consumed in large quantities over a short time, pose serious health risks to young children. That's why we're recommending that children under seven should not consume these drinks at all, and children aged 7 to 10 should have no more than one 350ml serving.'

The FSA says it will be monitoring the situation carefully and will take further action in the future if necessary.