We all might have happy childhood memories of playing in the ball pit at the playground, but a new study might just put you off letting your children dive in.
The US study found that children's ball pits are full of dangerous germs, some of which could be deadly.
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Published in the American Journal of Infection Control, the research found physical therapy clinics - and undoubtedly in public ball pits, too - were awash with "considerable microbial colonisation".
Almost all the pits tested were found to be contaminated with visible dirt, vomit, fences, or urine. Researchers found 31 bacterial species and one species of yeast.
Some of those bugs are responsible for pink eye, urinary tract infections, bloodstream infections, heart inflammation and more.
"Clinics may go days or even weeks between cleanings, allowing time for microorganisms to accumulate and grow to levels capable of giving children infections and making them sick," wrote senior study author Dobrusia Bialonska.
"Be aware of this if you take your child to a physical therapy clinic, especially if the child has a compromised immune system.
"You might consider asking for no treatment in the ball pit. We definitely showed that there are things on the balls that can potentially hurt a child who is immune-compromised."
It's not the first time ball pits have been identified as a playground for pathogens. A study on ball pits in 1999 also found high levels of bacteria were found in most of them.
"Disinfection protocol and proper handwashing are the keys to making ball pit play areas safe for children," the authors wrote at the time.