Any parent with school-age children will be familiar with slime. It’s the gooey super-stretchy sticky toy that comes in a rainbow of colours and textures. Kids love playing with it as it can be pulled and twisted into different shapes. Such is its popularity that slime has sparked a host of YouTube videos with people simply playing with it, and DIY videos on how to make it.

Over the safety limit

However, parents have been warned by consumer watchdog Which? to buy with caution after eight out of 11 popular children’s slimes were found to contain up to 4 x the EU safety limit of a potentially hazardous chemical called boron.

This means less than 30% of children’s slime met UK safety standards.

Safety recall

The testing led to major retailers, such as Hamleys and Amazon, removing these products from sale.

Which? sent its findings on to the Office for Product Safety and Standards and additionally called on the government to take action to safeguard the safety of children and better regulate the market.

Putty and slime

Furthermore, Which? warned some products were making it onto the shelves because they were marketed as putty instead of slime, as it allowed a higher level of boron content.

The EU safety limit is 300mg/kg for slime and 1200mg/kg for putty.

Activating ingredient

Many slimes use the mineral borax, which contains boron, as the activating ingredient, which gives slime its addictive slimy feel.

Boron is also used in products such as contact lens solution, laundry detergent and household cleaners.

The dangers

However, over-exposure to boron can cause skin irritation, convulsions diarrhoea, vomiting and cramps.

The European Commission have warned that very high levels of boron can affect fertility or cause harm to unborn children in pregnant women.

Problem for parents

The problem for parents is many slimes have little or no information about their ingredients, making it hard for parents to work out which ones are safe and which to avoid.

Full refund

Which? Suggest that parents who have already bought or own one of the slimes with dangerous levels of boron, should return it and get a full refund or replacement. Since it is in breach of safety regulations, it counts as a faulty product. This is regardless of whether it’s been opened or not.


If the slime has caused any harm to you or your child, you may be able to claim additional compensation via the Consumer Protection Act.

DIY warning

You may think making your own homemade version of slime will be less dangerous. However be aware that ingredients often included in DIY recipes, such as contact lens solution, also contains borax.

Safe alternatives

While these borax-based recipes are best avoided, there are natural slimes parents can make with their children, although the texture is notably different. Simply look on the Internet for recipes for edible slimes, made using alternative ingredients such as corn flour and water, and experiment with these.

Unsafe slimes

If you want to see which slimes passed and which failed, read more here: – Which?

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