What's inside your rubber ducky? The disturbing innards of your child's favourite bath toy

This is the true story of the ugly duckling: Dark mould could be multiplying inside your favourite bath toys. Armed with a craft knife and handsaw, this reporter took it upon himself to find out what bath users were really washing in. Should you be alarmed?

The rubber ducky and other toys are a mainstay of the Kiwi family bath time - but also a haven for mould and bacteria.

Being in damp, warm conditions means the toys - often used to suck in a squirt out water - can harbour hidden nasties.

The Herald put the call out to families willing to donate their beloved toys to science and sent some to a laboratory for testing.

Those results showed the bath toys contained "extremely high bacterial levels". Others were cut open, revealing insides completely covered in dark, gooey mould.

One parent was mortified by the inside of their child's rubber ducky - but don't fret bath lovers, experts told the Herald the mould was relatively safe.

Just how dirty are bath toys. Photo / Dean Purcell

While the slimy mould was "pretty gross", University of Auckland associate professor Siouxsie Wiles said it wasn't worth stressing about.

"I would say, for most healthy children, this is just natural exposure," she said.

"Unless the children have some kind of immune defect, but those parents should already be aware if they are vulnerable.

"[But it's] not worth getting all worried about - pretty gross, but there's so much gross stuff."

And when people don't have exposure to microbes - like mould - it is generally a bad thing as they helped train our immune system, Wiles said.

Meanwhile, director of Biodet Services, where five toys were sent for testing, Adrienne Burnie said the moulds were not toxic.

"If [the bather] had cuts and abrasions and things, it would add to the general soup in their bath but probably not to the extent of causing any real issues.

"There would perhaps be a low potential they could get a mild infection in a cut or graze - it would be reasonably low risk."

Associate professor Siouxsie Wiles from the University of Auckland. Photo / File

The toys sent to Biodet Services were tested for general bacterial analysis and escherichia coli - better known as E. coli.

Each toy was cut open, had its interior surface swabbed before the swab was placed into 100ml of sterile water and agitated.

Four out of five bath toys exhibited fungal growth associated with damp environments and contained "extremely high bacterial levels".

Meanwhile, either no faecal bacteria had survived until the tests took place or there was no faecal contamination at all, results concluded.

Bath toys which were unsealed should have any excess water tipped out and dried as quickly as possible to prevent bacteria growth.

Anyone who was unsure about the safety of their bath toy was advised to throw it out.

An owner of a rubber duck cut open, but not scientifically tested, was shocked when shown the insides of his daughter's bath toy.

Their 1-year-old would often put the toy in her mouth, with her father questioning: "I wonder if this is why she's so regularly sick during winter?"

This blue rhinoceros was full of black mould. Photo / Dean Purcell

However, his wife was far less concerned about the mould, saying: "She regularly eats dirt from the garden, I'm sure it's just building up her immunity."

In total, five toys were cut open, either by hand saw or craft knife depending on the thickness of the plastic, by the Herald and all but one had mould inside.

The one without was made of hard plastic and had no hole for water to get inside - another of hard plastic had a hole and was full of mould.

Meanwhile, the three remaining toys were squishy and all had small holes where water was able to get inside.

If people were worried about their bath toys, Plunket's national advisor Karen Magrath said they should either be cleaned or replaced.

They could be washed with a diluted bleach solution or even washed with hot water and soap to remove many of the germs.

For hard plastic toys, Magrath said to soak them for five minutes in a fresh bleach solution before letting them air dry.

However, her basic message was to follow general hygiene guidelines and use common sense.

"If you do suspect anything that looks unhygienic like discoloured water squirting out of a rubber duck, throw it out."

Other actions against mouldy bath toys

• Squeeze out water from the rubber ducks and toys with holes in them.

• Wash bath toys and put them out in fresh air and sunshine to dry completely.

• Holes in bath toys could be sealed shut with a hot glue gun or drilled larger for easy scrubbing.