Is Your Kitchen Sponge Safe?

A new study by the Mayo Clinic says your kitchen sponge is likely the germiest and dirtiest thing in your kitchen. In fact, if you use one, you may want to rethink your whole kitchen cleaning routine.

Why Sponges are Unsanitary

Most of us use one sponge for cleaning dishes, and another for wiping down countertops and other surfaces. The problem lies in the sponge's porous design, which allows food particles to become embedded, eventually becoming food sources for bacteria and viruses in an ideal damp environment. The more uneven the pockets on a sponge, the happier the bacteria.

And, there really isn't any way to clean them well enough to kill all the germs.

"It takes very high heat over an extended period of time to kill off many bacteria and viruses," says one Mayo researcher. "Even bleach won't get them all."

In fact, there are bacteria that thrive in the frozen tundra and in boiling hydrothermal vents, making your sponge like the Garden of Eden for viruses and bacteria. In a study at Furtwangen University in Germany, a microbiologist discovered 362 species of microbes in used kitchen sponges, and in some of the pores, the density of bacteria reached up to 54 billion individuals per square centimeter. 

Not All Bacteria are Bad

Bacteria exist everywhere—on our skin, in the soil, and in the air—and not all are harmful. Many perform vital jobs such as helping us absorb vital nutrients, produce vitamins, regulate our immune system, and protect us from harmful invaders. So, are the bacteria found in sponges worth worrying about?

In a word, yes. After studying and identifying as many of the bacteria in used sponges as possible (it is impossible to ID them all), researchers discovered that more than 50% were infectious, linked to food poisoning or severe sickness.

Adults with an underlying illness or compromised immune systems, the elderly, and young children are particularly susceptible to the harmful bacteria that grow on kitchen sponges. Healthy adults, however, are not as likely to get sick, but the E. coli and Salmonella bacteria brought into your home in foods and on packaging, deposited on your counters and in your sink, then wiped onto a sponge can make everyone sick.

So What Should You Do?

If you have to use a sponge because that's more satisfying, here are some steps you can take to make yours last longer:

• Put your sponge in your dishwasher each night and run it on a full cycle.

• Microwave your sponge for a full minute. This will kill most, but not all, pathogens.

• Don't store your sponge in the sink. Put it in a holder that will allow air to circulate around it so it dries faster.

• Wring out your sponge of as much moisture as you can when you've finished using it.

• Replace your kitchen sponge when it starts to smell bad. It's that easy. Bacteria smells bad, so use your nose to test your sponge and replace it when it stinks. This is usually every two weeks.

And, there are other options for having a mostly bacteria-free kitchen sink area:

• Use brushes instead of sponges. Brushes do not have the pockets where bacteria can grow and thrive, and they dry out much faster than sponges so the bacteria don't have the moisture they need to thrive. In fact, when the researchers introduced Salmonella to kitchen sponges, they thrived, but when they added these bacteria to brushes, they died. Natural bristles and synthetic ones are both fine.

• Use hydrogen peroxide to clean, not bleach. Bleach can be harsh and, unless left in contact with the bacteria long enough to work, is not as effective at killing them as hydrogen peroxide (and leaving bleach on anything for only a short while will probably damage it). Hydrogen peroxide is safe for disinfecting sinks (including stainless steel), color-safe for most surfaces, and non-toxic for humans and pets. Just don't mix vinegar with hydrogen peroxide as it causes a harmful toxic gas if inhaled. To use hydrogen peroxide, spray it onto the surface and leave for 30 seconds (something you can't do with bleach), then wipe off with a sponge and water.

If you use a sponge to clean your bathroom, you should follow the same routine as you would your kitchen sponges. Clean and healthy, as Martha would say, is a good thing.

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Sources: BBC, Mayo Clinic, Science News Today, Southern Living