The disturbing study found the dirtiest play pit had around 170,818 bacteria lurking per ball - whilst another had 712,000 microorganism cells.
An investigation of six children’s ball pits found more than 30 different kinds of bacteria hiding in play areas that can cause sickness in young kids.
Some pits had gone weeks without being cleaned - allowing them to become rife with germs.
American bods from the University of Georgia found pits riddled with bugs that have been linked with causing sepsis, meningitis or cause skin infections and pneumonia.
According to The Sun, researchers also spotted a yeast that causes fungal infections in people with weaker immune systems.
Germs linked to plants, dirt and food were also found during the study that can cause blood and skin infections or eye problems in babies.
The research, which was published in the American Journal of Infection Control, looked at ball pits in physical therapy centres in the US.
Ball pits are often used to help develop children's motor and sensory skills but they're also enjoyed in soft play centres and even family restaurants.
At each ball pit, researchers collected nine to 15 balls from different depths.
Researchers said they found “considerable microbial colonization in ball pits that were tested, including eight bacteria and one yeast that could cause disease".
Germs are particularly dangerous to young children if they get scratched limbs and scabby knees, just waiting for infections to pop up.
