The 5 Filthiest Household Items and How to Clean Them

Kitchen Sink and Sponge GermsNot all dirt is visible to the naked eye. And sometimes the most innocuous items in our homes can be the dirtiest.

Take, for example, the lowly kitchen sponge. According to a National Science Foundation International study, the kitchen sponge or dishrag is the single most germy spot in anyone’s home. And it resides in the dirtiest room in our homes. (Yes, folks, the kitchen outranks the bathroom and garage as residence of choice for the greatest number of pathogens—things that can make us sick.) At particular risk are pregnant women, the elderly, and people with compromised immune systems.

Other nests of nastiness in the room with the reputation for coziness and nourishment: the refrigerator meat and vegetable compartments, blender gaskets, can openers, rubber spatulas, food storage containers with rubber seals, and the coffeepot reservoir. We’re talking colonies of E. coli, salmonella, yeast, and mold.

So, in the interest of public and private health, here are the recommended ways to clean the top five household hotbeds of horror, courtesy of the NSF.

1. Kitchen Sponge/Dishrag

Sponges and dishrags can pick up bacteria during the cleaning process and, if not properly sanitized between uses, can be a prime spot for germ growth.

To clean: Place wet sponges in the microwave for two minutes once per day and replace often: every two weeks or more as needed. A better option for kitchen cleaning is dishcloths, towels, and rags. Sanitize them by washing on the clothes washer’s hot water cycle with bleach. Replace every one to two days.

2. Kitchen Sink

The second-highest concentration of microorganisms was found in the kitchen sink.

To clean: Wash and disinfect the sides and bottom of the sink one to two times per week with a disinfecting cleaner. Sanitize kitchen drains and disposals monthly by pouring a solution of one teaspoon of household bleach in one quart of water down the drain. Wash kitchen sink strainers in the dishwasher weekly.

3. Toothbrush Holder

The third germiest place in homes wasn’t actually in the kitchen, but the bathroom. And while many people would suspect faucet handles or light switches to be a germy place, toothbrush holders actually win the prize.

To clean: If dishwasher safe, place the toothbrush holder in a sanitizing dishwasher and wash one to two times per week. If not, hand wash with hot soapy water, rinse, then wipe with a disinfecting wipe one to two times per week.

4. Pet Bowl

If you have a pet, you probably need to know that pet dishes were found to be the fourth most germy place in the homes analyzed.

To clean: Pet dishes should be washed daily, either in a sanitizing dishwasher or scrubbed by hand with hot soapy water, then rinsed. If hand washing, place the dishes in a 1:50 bleach rinse (1 cap bleach in 1 gallon water) and soak for about 10 minutes once per week. Rinse thoroughly and allow to dry.

5. Coffee Reservoir

Given the dark, damp location, it’s a prime spot for bacteria, mold, and mildew to grow. Want sugar with that?

To clean: Follow the manufacturer’s recommended cleaning instructions. A common recommendation is to clean by adding up to 4 cups undiluted vinegar to the reservoir, letting it stand for 30 minutes, then running the vinegar through the unit. Follow this by running two to three cycles of fresh water through the unit until the vinegar odor is gone. Most manufacturers recommend cleaning every 40–80 brew cycles or at least monthly.

Although not all germs may cause health problems, proper cleaning of neglected or overlooked areas can help further reduce the risk of food-borne illness and infection.

Be aware of where the hot spots are in your home and be smart about protecting your family. For additional tips, contact the NSF Consumer Affairs Office at or download its Safer Home Kit.

NSF International is an independent, not-for-profit public health organization that certifies products and writes standards for food, water, and consumer goods. It has a 65-year history of protecting public health and safety worldwide.