My approach to replacing the sponge I use to wash dishes is less about time frame and more about when it looks manky.
Sarah McLean, a lecturer in environmental health at Swinburne University of Technology, says that's probably not a satisfactory guide.
Dr McLean says bacteria, and sometimes even viruses, can live on the tools we use to wash dishes — whether that's a sponge, brush, or cloth.
"It's one of those tricky things, because you want to be sustainable, but you also don't want to put yourself or family at risk" by using these items for too long, she says.
So, how often should we be changing or cleaning the sponges, brushes, and cloths we use to wash dishes?
What lives on our dishwashing tools?
Researchers have found 362 different species of bacteria can live on kitchen sponges, according to a 2017 study published in Scientific Reports.
Ramon Shaban, the clinical chair of infection prevention and disease control at Westmead Hospital and the University of Sydney, says "lots and lots of germs" such as salmonella and E. coli can be present on washing-up equipment.
"These are bugs that usually cause diarrhoeal kinds of diseases," Professor Shaban says.
Dishwashing cloths face a similar fate as sponges, says Dr McLean, due to both being absorbent and often staying damp between uses.
Brushes, however, are proven to harbour fewer germs.
A 2022 study published in the National Library of Medicine found lower bacterial levels were observed in used brushes than in sponges, and that salmonella the researchers added "died more rapidly in brushes".
"The bristles in the brush are able to dry more quickly, so the bacteria is more likely to die out," says Dr McLean.
How often should we change or clean our dishwashing tools?
How often you need to change kitchen sponges will depend on how frequently they are used and what for, our experts say.
"The first golden rule is to follow the manufacturer's instructions," Professor Shaban says.
Failing that, our experts recommend they should be disposed of every one to two weeks.
"If you're going to use a kitchen sponge more than once, make sure you thoroughly rinse it and hang it to dry — bugs grow when it's a damp environment," Professor Shaban says.
Cloths, if reusable, can be thrown into your washing machine for a thorough clean.
Brushes can generally last "weeks, even months", Professor Shaban says.
To get longevity out of brushes, Dr McLean recommends boiling them or running through the dishwasher [if you have one] to kill bacteria.
Professor Shaban says it really comes down to people just being mindful about how they use sponges and other washing tools.
For example, don't wipe up after chopping raw chicken with the sponge you wash your dishes with.
"Use a disposable paper towel instead," he says.
Don't forget about tea towels
Dr McLean says we can't overlook tea towels when talking about items used in the kitchen, as they can be "particularly nasty".
"We tend to use them when we are cooking to wipe our hands in between handling different products … and then drying dishes.
"Bacteria love to grow on tea towels."
She recommends having separate towels for cooking and drying dishes.
Professor Shaban says we should wash tea towels at least as frequently as our bath towels.
Ultimately, as long as we are careful with how we use these items in the kitchen, we don't need to be too worried.
"Certainly bacteria could potentially be transferred [from the tools] and if there were any pathogens there, you might end up ingesting those, but it's pretty low risk," Dr McLean says.
