Children's slime keeps failing Europe's boron limit, most often when it comes from unknown online sellers

Updated 18 October 2026.

Slime gets stretched, squashed and passed from hand to hand, and children's hands soon find their way to mouths and snack bowls. Hong Kong's Consumer Council warns that children who touch their mouth or food after playing with a toy high in boron, without first washing their hands thoroughly, are at risk of ingesting the chemical.¹ So the boron that matters is the boron that travels from fingers to mouth.

Denmark's Consumer Council bought 16 toy slimes on online platforms, and 10 of them had boron release far above the toy limit.² Boron is a chemical in borax, a common slime ingredient that helps create its stickiness, and toy slimes may release no more than 300 milligrams of it per kilo of slime.^3,4,5 From shops on the Danish market, only one product exceeded the limit, while a few were just around the limit.²

The Danish result is not a one-off. In the EU's coordinated check of slime toys, national market inspectors tested 180 samples and found 47 that did not meet at least one requirement, 46 of them for boron.⁶ Nor is it new: in a test from 2018, Denmark's Consumer Council found that six of 15 toy slimes from the Danish market had boron release just around or above the toy limit.²

Germany's Federal Institute for Risk Assessment (BfR) puts the chance of acute, sudden harm to a child from boron in slime at very low.⁷ But too much boron may impair fertility and cause harm to unborn children, Which? notes.⁵

In everyday terms, a single pot over the limit is very unlikely to make a child ill. But the tests we read do not measure what months of daily play add up to, so we would still choose slime that stays within the limit.

YAN's view: a toy children squeeze and stretch for hours should stay under the boron limit every time, and since you cannot check that on the shelf, we would buy slime only from a shop that answers for what it sells, and keep it away from mouths, food and children under three.

What you need to know

• Slime bought outside the EU or on online platforms failed far more often than slime from local shops.^2,8
• German risk assessors rate the chance of sudden harm as very low, but too much boron may impair fertility.^5,7
• Wash hands after every play session and before eating, keep slime out of mouths, and don't give it to children under three.
• Buy from a local shop that names the maker and prints an age warning; skip pots from unknown sellers abroad.

What is slime, and what do the rules say?

A separate survey by Denmark's environment agency bought 27 slime products in Denmark, elsewhere in the EU and outside the EU, measured how much boron seeps out of each one, and found boron coming out of all 27.⁸

Check the pot for a warning that it is not suitable for children under three, because slime is not a toy for that age. The label is there because toddlers put things in their mouths, but it cannot stop a younger child from reaching an older sibling's pot.

How worried should you be?

Exposure to too much boron can cause irritation, diarrhoea and vomiting in the short term, Which? notes.⁵ BfR is also plain that manufacturers are obliged to comply with the legal limit values for boron.⁷ So a pot over the limit is not a grey area: it should never have been on sale.

Why does where you buy it matter?

Denmark's environment agency found the same split: most of the slimes it bought outside the EU did not comply with the law, a far higher share than those bought in Denmark.⁸ The agency concluded that more products purchased outside the EU may pose a health risk than products purchased within the EU.⁸

“Consumers simply cannot be sure of products bought on online platforms where the seller is from third countries,” said Minister Magnus Heunicke.²

Take the one product from the Danish market that went over the limit.² One shop told the Danish Consumer Council it had stopped selling the product until it knew more from the manufacturer.² That is the advantage of a shop you can name: when a problem is found, someone answers for it.

So the worse buy is clear: slime from an unknown seller abroad, ordered through an online platform, is far more likely to break the boron limit than a pot from a local shop. A local shop is the better choice, not a guaranteed one: some slimes from shops in Denmark and elsewhere in the EU still failed, and others sat right at the limit.

What happens when a slime fails?

In Britain, one slime sold in a shop was found to contain more boron than the law allows, and the stock was seized from the shop that sold it.⁹ Another, a sensory slime set sold in Britain, was recalled from the people who had bought it because its coloured slime had too much boron.¹⁰

European consumer groups have found that online platforms where slime is often sold do not systematically withdraw faulty batches that officials have reported.¹¹ “This clearly shows that there is an urgent need for the platforms to take greater responsibility for their products than they do today,” said Stine Müller of Denmark's Consumer Council, “if we are to adequately protect children and limit their exposure to unwanted chemicals.”²

A recall only protects a child if the family hears about it. To check a pot you own, search its name on the UK government's product safety alerts and recalls page or the EU's Safety Gate site.

What if it says putty?

The EU safety standard says toy slimes must release less than 300 milligrams of boron per kilo of slime (written 300mg/kg), while toy putties may release up to 1,200mg/kg.⁵ So the group a product falls into matters: a slime judged as a putty would face a far looser limit. Two makers whose products Which? classed as slimes argued they were putty and so passed the EU standard, but Which? stood by its accredited laboratory's decision.⁵ A technical specification has now been issued to help sort slime type products into the right category when they are tested.¹² So go by what the slime does, not what the pot calls it: if it is runny, stretchy and sticky, treat it as slime.

What nobody has tested

Every test we read checked a sample against the legal limit. What the tests we read do not show is how much more a toddler takes in by mouthing slime, or whether boron release changes as slime ages and dries out. And a pass speaks for the sample that was tested, not for every other pot of the same slime.

If studies of real daily play showed children's boron intake staying well below safe levels, or if repeated market checks found slime reliably under the limit, we would ease this advice.

What to choose

Make hand-washing the end of every slime session, and always wash before snacks or meals. Play at a table away from food, keep slime out of mouths, and put the pot away when younger children are around. Don't give slime to children under three, whatever the pack says.

Throw slime away when it dries out, smells odd, changes colour or grows spots, rather than keeping one pot going for months. That habit is worth keeping because slime can grow germs: Hong Kong's Consumer Council found two slimes with germ counts far above the limit the EU recommends, and none of the slimes it tested gave an expiry date.¹

Skip slime from unknown sellers abroad on online platforms, however cheap or colourful. Buy from a shop in the UK or EU that you could take it back to, and choose a pack that names its maker and carries an age warning and instructions. In the same EU check of 180 samples, many also failed on their warnings, markings and instructions.⁶ So put back any pot that lacks them.

If your child already has slime from a local shop, there is no need to bin it today: keep the habits above and replace it when it dries out. If it came from an unknown seller abroad and gets played with every day, we would replace it with one from a local shop; if you can't, keep play short and hands washed.

Slime is a short-lived toy: it cannot be repaired or recycled, and when it dries out it goes in the household bin. We prefer toys built to last from materials we can account for, so at YAN we would buy slime rarely, from a seller who answers for it, and treat it as an occasional messy treat rather than an everyday toy. Our research found no tested alternative we can recommend in its place, so if your child loves the squish, the habits above matter more than the brand.