Learn why—and when—to discard a kitchen sponge before it can do more harm than good.

It’s one of your handiest cleaning helpers—soaking up spills, banishing crumbs, scrubbing sinks, even washing dishes. It’s the common kitchen sponge, and there’s probably one sitting nearby your drain board right now. But before you grab it to make short work of the latest everyday mess, ask yourself when you last swapped it out for a new one. Can’t remember? You’re not alone—after all, sponges are reusable.

However, all good things must come to an end, especially when you consider that this study found that a kitchen sponge is better for growing bacteria than a Petri dish. Keep reading to learn what problems can arise from a sponge past its prime, how to extend its lifespan, and when to toss it for good.

Understanding the Sponge

Most household sponges available on supermarket shelves are made from either polyurethane (a petroleum-based product) or cellulose (a natural material derived from wood pulp). Both boast an absorbent quality that makes them effective at removing and collecting grease, grime, gunk, and other unwanted substances from common surfaces. What makes sponges so much better than the average paper towel or rag is that they can soak up water and cleaning product and hold their shape well even after a good scrubbing.

But that absorbency also provides the warm, moist conditions that act as a welcome mat for microbes. Food particles can hide in a sponge’s porous fibers, nourishing germs and mildew. While some of the stuff accumulating on the average sponge will be harmless, some could lead to illness—notably salmonella, staphylococcus, E. coli, and listeria.

No surprise, since sponges are often employed after food prep, cooking, and eating, so they are exposed to raw meat, dirty produce, and who-knows-what on the hands and in the mouths of folks around the dinner table. And let’s not even discuss what bathroom sponges encounter.

How Long Is a Sponge Safe to Use?

To keep sponges safe and functional, many people choose to sanitize them after daily use. One common method is to soak a sponge in a one-to-nine bleach-to-water solution for several minutes, then rinse, wring, and air dry. Other approaches rely on high heat: popping a wet sponge in the microwave for two minutes, boiling it, or adding it to a dishwasher cycle. However, while sanitizing can banish a lot of nastiness, it will not expunge a sponge entirely—some of the most pathogenic bacteria may still stubbornly cling to it.

Sponges don’t have an expiration date, and we all use them differently, which means there’s no hard-and-fast rule to determine how long you can safely use one. As the USDA ambiguously puts it: “Kitchen sponges are potential sources of bacteria and are difficult to clean. Microwaving or boiling kitchen sponges may reduce some of the bacterial load; however, these methods alone are not adequate to ensure that your sponge will reduce potential cross-contamination of hands, kitchen counters, and food. If you use sponges, buy new ones frequently.

Cleanliness conservatives may throw away a sponge after only a week or two of use, the less germ-a-phobic among us may keep it around for a month or more, and the truly cavalier may work that sponge until it starts to look dirty and smell bad.

How to Squeeze More Life Out of a Sponge

There are ways to extend a sponge’s usefulness while hedging your bets against it causing illness:

Isolate your sponges

Avoid cross-contamination by dedicating one sponge exclusively for dishes and another for kitchen surfaces. Keep them in separate, preferably aerated, holders as well—upright if possible—rather than side by side.

Sanitize after use

Though sponges are often used with dish detergent or multi-purpose cleansers, these products can’t be counted on to clean—much less disinfect—a sponge. Daily sanitizing (as described above using bleach, the dishwasher, or the microwave) is better than merely rinsing after use.

Give them the snip

Sponges come in different shapes and sizes, but an average 3 X 4 ½ inch rectangular sponge can easily be cut in half before use, giving you two sponges instead of one.

Make a biodegradable choice

If the germ factor of sponges hasn’t led you to swear off them completely, you may opt to toss them more frequently. In that case, consider using biodegradable sponges—those made of cellulose, bamboo, or hemp—as opposed to synthetic ones, which can last in landfills for centuries, if they decompose at all. Natural sponges may not be any safer for your household, but they certainly are healthier for the planet.

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