How Often Should You Replace Your Kitchen Sponge?
By the Q Bio Acupuncture Clinic care team · Koreatown, Los Angeles
Quick answer
When researchers analyzed 14 used kitchen sponges, they found them densely packed with bacteria, and the research team suggested replacing sponges about once a week [1]. Microwaving sharply reduced bacteria in a lab test [2], but whether the changes seen in sponges microwaved regularly at home are good for hygiene is not yet known [3].
What the studies found
Using DNA analysis and microscopy, researchers found bacteria clustered on the surfaces and inside the hollow spaces of 14 used sponges, at densities of up to 54 billion cells per cubic centimeter [1].
Sponges that their owners said they cleaned regularly had a different mix of bacteria, and some bacterial groups made up a larger share, not a smaller one [1]. Bacterial counts from microscope images were not significantly lower either, although this did not measure the total bacteria in the whole sponge [1].
In a 2006 experiment, sponges deliberately contaminated with wastewater were microwaved at full power in a household microwave, and total bacteria dropped sharply within 1–2 minutes [2]. Spores of some bacteria survived longer than other microbes [2].
In a 2020 study, sponges microwaved 2–3 times a week had a different bacterial makeup and metabolic profile than untreated sponges, with a higher share of some groups, including Salmonella [3]. The researchers said follow-up studies are needed to know whether this change is good or bad for hygiene and health [3].
Practical tips
When deciding how often to replace your sponge, the one-week interval the researchers suggested is a useful reference point.
Put the replacement date on your calendar or set a phone reminder so it is easy to keep track.
If you want to microwave a sponge, check the instructions from the sponge and microwave manufacturers first.
Frequently asked questions
Does microwaving kill all the bacteria?
Sponges contaminated in the lab showed a large drop in bacteria within 1–2 minutes [2]. But sponges microwaved 2–3 times a week at home ended up with a different bacterial mix, and what that means is not yet known [3].
If I clean my sponge, do I still need to replace it?
We did not find a study that directly compares cleaning with replacing. One research team questioned the long-term benefit of regular cleaning and suggested replacing sponges periodically [1].
What if I am worried about my health?
This article shares everyday hygiene information. If you have symptoms or an ongoing health condition, please talk with a qualified professional.
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Korean version: 주방 수세미, 얼마나 자주 바꿔야 할까?
Sources
Cardinale M, et al. Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by Acinetobacter, Moraxella and Chryseobacterium species. Sci Rep. 2017;7(1):5791. PMID 28725026. https://pubmed.ncbi.nlm.nih.gov/28725026/
Park DK, Bitton G, Melker R. Microbial inactivation by microwave radiation in the home environment. J Environ Health. 2006;69(5):17-24. PMID 17190338. https://pubmed.ncbi.nlm.nih.gov/17190338/
Jacksch S, et al. Metagenomic Analysis of Regularly Microwave-Treated and Untreated Domestic Kitchen Sponges. Microorganisms. 2020;8(5):736. PMID 32423128. https://pubmed.ncbi.nlm.nih.gov/32423128/
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