School play equipment poses a potential infection hazard for young children, a study suggests.
Testing for germ "hot spots" at two typical UK schools revealed high levels of bacteria in unexpected places.
Play equipment had more bugs on its surfaces than did door handles, radiators, stationary items and chairs.
At one school a "play" dinosaur registered a contamination reading 41 times higher than that obtained from a toilet door.
Experts from pest controllers Rentokil swabbed 130 locations at an infant and primary school in the south of England and tested the samples using a hi-tech microbe detector.
From the results, they produced contamination "heat maps" showing the dirtiest areas where cleansing was most needed to prevent outbreaks of infection.
Luke Rutterford, technical manager at Rentokil Specialist Hygiene, said: "These findings may surprise many, as it is not necessarily the objects and areas they would associate with being unhygienic such as toilets, but instead items that are shared and used by multiple children which appear to be harbouring the most germs.
"Play equipment and shared items such as pens and pencils, are used regularly throughout the day but rarely cleaned, providing lots of opportunity for cross contamination."
Bacterial contamination was measured as units, with the normal range falling between 200 and 500. A reading of 500 units or above is considered "high".
Across the two schools, the top five hot spots hosting the most bugs were play equipment, with an average of 2,857 units, door handles (985 units), radiators (743 units), stationery (675 units) and chairs (669 units).
The dinosaur registered 7,760 units, a reading more than 15 times the top of the normal range.
One especially affected infant school reception classroom contained a mascot teddy bear that registered 2,492 units. A reading of 3,885 units was obtained from a sink in the same room, and 2,271 units from a door handle.
Both schools co-operated willingly with the tests but chose to remain anonymous.
The technique used, called ATP bioluminescence, measures light given off when a biomarker reacts with a firefly enzyme. The marker is adenosine triphosphate (ATP), an energy molecule in all living cells including bacteria.
ATP is not found in viruses, so the technique cannot detect viral contamination directly. But the bacterial hot spots identified by the test are also the most likely to harbour infectious viruses.
Mr Rutterford added: "Heat maps help us to visualise which areas need a specialist 'manual' deep clean, compared to other areas where an ultra low volume fogging treatment may suffice.
"Accurately heat mapping a school's microbiological landscape enables informed decisions to be made on where and how to clean.
"In turn, this could ensure that any outbreaks of highly contagious illnesses such as norovirus are contained sooner and significantly reduce the levels of pupil and teacher sickness."
ATP testing forms part of Rentokil's new Hygiene Healthcheck service aimed at education facilities, care homes, leisure centres and offices.