The kitchen sponge is a tiny workhorse that takes on everything from greasy pans to quick countertop wipe downs. The problem is that its soft, porous structure creates the kind of damp hideout microbes love. Once you start thinking about what gets trapped inside, that innocent little block can feel a lot less harmless. A closer look at what researchers have found may change how long you keep one by the sink.
A 2017 study led by microbiologist Markus Egert at Furtwangen University in Germany found that used kitchen sponges can be packed with microscopic life. Researchers identified 362 different types of microbes, and in some areas the concentration reached about 54 billion bacteria per square centimetre. The study also noted that five of the ten most common bacterial groups on sponges were closely related to ones that can cause infections in people with weakened immune systems. It is the kind of statistic that makes you want to retire your sponge immediately.
If your first instinct is to sanitize it, the findings get even more unsettling. Egert’s research suggested that common “fixes” like washing a sponge with hot water and soap or microwaving it do not always solve the problem, and could even encourage certain bacteria to multiply. That does not mean cleaning is pointless, but it does suggest a sponge is hard to truly reset once it has been in heavy rotation. In other words, a sponge can look clean while still hosting an invisible crowd.
Food safety expert Jennifer Quinlan, a professor at Prairie View A&M University in the US, offers a more practical middle ground. She recommends two simple ways to reduce bacteria between replacements, running the sponge through the dishwasher at the end of the evening or microwaving it for about a minute until you see steam. The goal is not to make it sterile forever, but to cut down most pathogens for a short window. It is a helpful habit during busy cooking stretches when you cannot swap supplies right away.
Egert also stressed that his team did not find bacteria typically linked to food poisoning in healthy people, which is a reassuring detail. Still, his advice is blunt, he would skip kitchen sponges entirely and use a dish brush instead, since brushes dry more easily and do not hold moisture deep inside the way sponges do. Quinlan’s simpler rule is to replace a sponge once a week, even if it seems fine. Between weekly swaps, a quick dishwasher cycle or a brief steam in the microwave can help keep things more under control.
Do you replace your sponge regularly, prefer a dish brush, or have a cleaning routine you swear by, share your thoughts in the comments.
