Q. I know the kitchen sponge grows bacteria. I have been putting it in the microwave for 30 seconds with the expectation that zapping it will kill the bacteria. Do you think this is effective?

A. Several years ago we found an article in the Journal of Environmental Health (Dec. 2006) that suggested wetting a sponge and nuking it in the microwave for one to two minutes at 1100 watts of energy to kill lingering germs.

One reader who tried this reported: “We microwaved our WET sponge this morning and it caught on fire. Now our house smells terrible. It was scary and annoying at 6:30 am!”

Scientists have published on the pros and cons of using microwave disinfection for dentures (Journal of the American Dental Association, March 2012) and toothbrushes (American Journal of Dentistry, June, 2011). Toothbrushes are best disinfected by soaking in Crest Pro-Health mouthwash for 20 minutes or by running them through a normal dishwasher cycle. For dentures, microwave treatment for three minutes at 650 watts was effective, as was a 10 minute soak in chlorhexidine solution (e.g., Peridex).

We have not seen a comparative study for kitchen sponges, but running the sponge through a regular dishwasher cycle might be a good approach for disinfecting it, as well.

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  1. abigail

    If a sponge or dish cloth has odors, chances are the items it was used on are not clean after being washed. It might help to wash dishes with plenty of detergent or soap in the hot water, rinse them off, rinse again in a bowl of water with a good splash of vinegar in it.
    If dishes etc, have to sit awhile before washing, rinse all food off before letting them sit and wash and rinse out the sponge/cloth frequently while working. Sometimes if greasy food is being cleaned off, the sponge just doesn’t feel clean again. If vinegar doesn’t help, it’s time to ditch it. less expensive than getting sick. A good pair of latex kitchen gloves makes it possible to use very hot water for dishes.

  2. RAW

    A ‘radio doctor’ mentioned putting sponges in microwave for two minutes to kill germs. I have been doing so for many years– have never had a fire or any other problem. After the two minutes I take sponges out (careful, they are hot), grab a paper towel and wipe out the microwave. Clean sponges and clean microwave at the same time. I also like the disposable disinfecting handi- wipes. Good for a quick clean up of kitchen and bath room counters.

  3. Beach Bouy

    I nuke my dishrag all the time. I read a report a couple of years ago that said nuking your wet dishrag or sponge would kill 99 percent of the bacteria. However, this also cooks the food particles trapped in the fabric or sponge cells and could eventually cause an unpleasant smell. So, even after nuking, the cloth or sponge needs to be washed thoroughly and rinsed at the sink after it cools down from the nuke job.

  4. LF

    Seriously, people, like others have said—I probably own 10 decent sponges for washing dishes. I use one per day and then it goes into the mesh bag with a load of towels with bleach. Don’t make this harder than it needs to be.

  5. Rita

    I always use the microwave with my damp dishcloth for 3 minutes. No fires ever happened.
    I used to always have food particles left over in the dishwasher until we finally cleaned the filter!! I would try that before calling a repairman or buying a new dishwasher.

  6. RM

    I have been microwaving kitchen sponges for years and it works like a charm. I’ve found that putting the wet sponge in for 30 seconds in an 1100 watt microwave (with turntable) seems to work fine. Rinse the sponge and squeeze most of the water out before microwaving. The key is to raise the temperatures throughout the sponge to the level of very hot (but not boiling) water, which cooks and kills the bacteria. After 30 seconds of microwaving, let the sponge sit for 30 seconds or so to cool down so you can take it out. It will be hot, so use caution.
    The proof is in the smell — a smelly sponge has food particles in it which are growing bacteria. After a microwaving, smell the sponge — if the smell is pretty well gone, so are the bacteria (at least until you wash dishes with it again). If it is only just warm to the touch, or still has a smell, give it another zap. After a sponge has been through a few of these cycles, it’s probably time to toss it out and use a new sponge.
    We’ve been using blue Scotch Brite sponges which don’t list any antibiotic ingredients. (CAUTION: If you microwave any plastic item for too long, it could possibly melt or catch fire (frozen dinners included), so putting a sponge in the oven for minutes of microwaving is definitely not recommended.)

  7. Fran

    I have been putting my sponge in the dishwasher for years and then 1 min. in the microwave – works great.

  8. Nancy D

    Your dishwasher should not be leaving any food residue… You might want to check with an appliance repairman for his input, but Methinks you need a new dishwasher! nd

  9. PP

    When I run the diswasher I soak brushes and scrubbies in a bleach solution overnight, then rinse in hot water so as not to get any of it on the clothes. That’s the time to give give the sinks and counters a good scrub and disinfecting, as well as changing the towels and dish rag.

  10. EQB

    I put my sponges into a mesh washing bag and throw it into the washing machine bleach load each week. They come out great.

  11. VFC

    I haven’t used sponges in eons, they have always smelled to me and just look like a petry dish. I use the disposable Handi Wipes- they dry quickly hung over the faucet and a squirt or two of bleach cleaner and it’s done. Sops up just as much water as a sponge. Why worry about calculating microwave time or falling into the dish washer coils? Repairmen are too expensive!

  12. Melinda

    Why not just run them through the washing machine and dryer with the towels. I wash them all on hot and dry them that way, too.

  13. Mikey

    I can’t believe the germ paranoia in this country lately. I ate dirt as a child, and probably continue to get my share of it. I’ve never cleaned a toothbrush in my life. Kitchen sponges do begin to smell after a couple of weeks, though, and get an overnight soak in a weak Clorox solution.

  14. cpmt

    what about bleach? I always do it in water+ bleach. I hope this works!! . Still I think it is a good idea to begin to wash them (now) in the dishwasher.

  15. kaf

    We discovered about 2 years ago, that all the sponges at our grocery store were pre-treated with the anti-biotic microban. As we weren’t excited about exposing ourselves to this, we started to dishcloths again. After use, they are easily washed in the washing machine. In our house, 2 or 3a day is not uncommon.
    After a bad cold, I throw out my toothbrush and get a new one. They’re cheap enough and I don’t get that many bad colds.

  16. wj

    I have always used new sponges to solve this problem.

  17. Sheila

    I sprinkle my sponge on both sides with baking soda and then pour vinegar over the sponge. It works like a champ every time and gets rid of the smell completely.

  18. s.h.

    re:cleaning a sponge, etc. Someone mentioned putting toothbrushes in dishwasher through a cycle. ewwww. there is always some residue of teeny little food particles, or worse, left in the dishwasher even at the end of the last rinse.
    I disinfect my tooth brushes the way my old timey eye doctor told me to disinfect my soft contact lenses, after a bad cold, flu, etc. Buy the peroxide cleaner for contacts. For toothbrushes, I soak in 3% drug store hydrogen peroxide for the same 10 mins that were required to disinfect contacts. In fact, I soak brushes once a week in peroxide. and as for the peroxide for contacts? There is a soaking solution that is purified h2o2 that comes with a soaking holder that has a little piece of black metal or plastic to make the peroxide inert and plain sterile water at the end.
    I would imagine that soaking sponges in a glass bowl in hydrogen peroxide would work great. Maybe, even soaking the sponges in white vinegar would work; (I was told years ago by a nurse visiting Russia on a medical missions trip that hospitals there were so poor that doctors and nurses used vinegar for disinfection; it is probably 5% strength), but I would give the peroxide a try; cheap, cheap, cheap, usually less than 1 dollar.

  19. Corinne

    Just be careful about putting sponge in dishwasher . . . it could end up on the drying coil at the bottom and catch fire. Then it will be REALLY sterile!

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