Dishwashing Sponge Turns Out to Contain Billions of Bacteria, Researchers Reveal

JAKARTA - The kitchen sponge that has been used to clean dishes, glasses, and cutlery turns out to store a very large number of bacteria.

A study has found that used kitchen sponges can contain bacteria in amounts equivalent to human faecal samples, raising concerns about the hygiene of everyday household items.

Research conducted in 2017 by Markus Egert, a microbiologist at Furtwangen University, Germany, revealed that kitchen sponges are an ideal environment for the growth of microorganisms. Their warm, moist, and full of food waste conditions make them the perfect breeding ground for various types of bacteria.

In his study, Egert analyzed the microbiome of the former kitchen sponge and found as many as 362 microbial species. In some parts of the sponge, the bacterial density reaches 54 billion individuals per square centimeter.

"This number is very large, similar to the number of bacteria found in human stool samples," said Egert, quoted from the BBC website on Saturday, May 16, 2026.

According to Egert, the sponge's structure filled with small holes and cavities allows various microbial communities to live and thrive simultaneously. Each cavity creates its own micro-environment that supports the growth of bacteria with different needs.

This finding was reinforced by a 2022 study conducted by Lingchong You, a synthetic biologist from Duke University, and his team. They found that sponges with a variety of pore sizes actually promoted higher microbial growth.

"They found that the variation in pore size in the kitchen sponge is crucial in promoting bacterial growth," Egert said.

Even though the number of bacteria is very large, the researchers emphasize that not all of these bacteria are harmful to humans. In Egert's study, no direct relationship was found between the bacteria in the sponge and food poisoning or serious diseases.

However, five of the ten most common bacterial species found have close relationships with bacteria that can cause infections in people with weakened immune systems.

"We only found bacteria that are potentially pathogenic. This can be dangerous for people with weak immune systems, the elderly, or children. Usually, for healthy people, bacteria in the kitchen sponge are not harmful," concluded Egert.

Another study in 2017 by Jennifer Quinlan, professor of food safety at Prairie View A&M University, United States, found that only about 1-2 percent of kitchen sponges from 100 houses studied contained bacteria that cause food poisoning in humans, and the number is relatively small.

Even so, there is still a risk, especially if the sponge is used to clean liquids from raw meat or raw chicken that may contain pathogens such as Salmonella.

"Most of the bacteria on the sponge do not cause disease, just make it smell. However, it is possible that pathogenic bacteria appear if the sponge is used to clean raw meat or raw chicken liquids," said Egert.

Another study by Nofima scientist Solveig Langsrud, also from Norway, showed that bacteria such as Salmonella can thrive on sponges, but do not survive on dishwashers because the tools dry out faster.

On this basis, a number of experts suggest changing the kitchen sponge more often and keeping it clean. The sponge should be dried after use, not stored in a wet condition in the sink, and replaced periodically, ideally every week.

Egert openly recommends using a dishwashing brush as an alternative.

"I won't use a dishwashing sponge. A brush is much better because it contains fewer bacteria, dries faster, and is easier to clean." he said.