Which are the germiest spots in your house?

You may know the worst, but you’re probably not even thinking of the fifth most germy.


NSF International visited 22 Michigan homes a few years ago and took swabs of the 26 locations thought to be the most touched by people living there. These are the places where we pick up germs or leave germs behind for other family or friends to contact.

Many bacteria are harmless or maybe even helpful, of course, but some might be the sources of illness, including foodborne illness. NSF is a product testing, inspection and certification organization.

The researchers then measured the concentration of bacteria they collected from each spot.

The germiest place

The highest concentration by far they found was on dish sponges. That shouldn’t come as a surprise.

“Sponges come into contact with food residues that can build up in them and that provide nutrients for bacteria and other microorganisms to grow,” explains microbiologist Manan Sharma of the United States Department of Agriculture’s Food Safety Laboratory in Beltsville, Maryland.

What’s more, sponges are often wet and are left in damp areas in or near the sink, which are ideal conditions for germs to multiply.

“They also have many nooks and crannies, which can be great places for germs to multiply,” notes NSF microbiologist Rob Donofrio, who adds that “sponges are typically not properly— or regularly—sanitized before their next use.”

Next most germy in the NSF study:

Toothbrush holders. Then came the pet’s bowl and the kitchen sink.

“Sink drains are really dirty places,” says the University of Georgia’s Joseph Frank. Food particles get trapped in the drain and disposal, creating a perfect environment for bacterial growth.

“You’ll find Listeria in a good many drains, and probably Salmonella too, especially if people use the sink for rinsing off raw meat or poultry,” says Frank.

And the fifth highest concentration of bacteria?

The coffee reservoir, where you pour the cold water into a drip coffee maker. It’s a good bet that most people don’t think of their coffee maker as one of the germiest sites in their house.

Coffee makers “are certainly a moist environment where mold and bacteria are known to grow in high numbers,” Kelly Reynolds, who studies household germs at the University of Arizona, told the Huffington Post. “Our bodies can deal with them, but at some point they’ll grow to levels high enough to cause sickness.”

How to clean your coffee reservoir?

Here’s the advice of the Good Housekeeping Institute:

  • Fill the reservoir with equal parts vinegar and water,
  • place a paper filter into the machine’s empty basket,
  • position the pot in place and “brew” the solution halfway,
  • turn off the machine and let it sit for 30 minutes,
  • turn the coffeemaker back on and finish the brewing,
  • dump out the full pot of vinegar and water,
  • rinse everything out by putting in a new paper filter and brewing a full pot of clean water,
  • repeat once.

What were the next germiest spots in the houses that NSF sampled? The kitchen countertop, stove knobs and pet’s toy. Then came toilet seats and bathroom faucet handles. In fact, overall kitchens had more bacteria than bathrooms. Yikes!

Among the objects with the least bacteria: purses, wallets, remote controls, and cell phones.


Source: J. Environ. Health. 75: 12, 2012.

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