Loom bands cancer fear

And as the craze gets more creative, children have recently been able to buy small plastic charms to add to their bracelets. And it’s these decorative charms that were found to contain high levels of phthalates, which enter the body through contact with sweat or saliva.

The good news is that it's not the loom bands themselves, and it's only the cheap, imported charms that are potentially dangerous.

The use of phthalates is strictly controlled – but imported charms were found to have 500 times the accepted level by The Birmingham Assay Office, an independent company that tests the safety of toys.

It tested 16 packets of the charms from cheaper “unofficial” box sets and found they all contained more than the 0.1% accepted level for phthalates. Two packets contained more than 50% phthalates.

"It's not to say every packet of loom bands out there is affected but there are plenty of products on the market that could be dangerous,” Marion Wilson, from the Birmingham Assay Office told the Telegraph.

"The worrying thing is the charms are the bits that are most likely to end up in children's mouths."

How can you know you're buying the safe ones?

Parents are now being urged by Trading Standards to make sure they only buy loom band products stamped with the CE safety mark.

"Loom bands and their charms are very cheap to make. They are flooding into Britain in their millions and it is very hard to keep tabs on them," explains Robert Chantry-Price, a lead officer for product safety at the Trading Standards Institute.

"I would warn parents to be vigilant about loom bands - only buy from a respected shops, not off market stalls, and look for a UK distributor's address on the packing as well as a CE mark. Don't allow your children to put them in their mouths."

Read more:

* Why loom bands are being banned at schools

* Loom bands: new craft ideas

* Do children need educating on cancer?