It's amazing Charles Gerba can stand to touch anything. A professor in the department of soil, water and environmental science at the University of Arizona, Gerber is an internationally recognized environmental microbiologist or germ expert.

He got into the whole bacteria business way back when he was a child. Gerba earned the nickname "Dr. Germ" for his expertise — and his love — for all things hygiene-related.

"When I was a little kid I wanted to be a chemist and told my mom I wanted a chemistry set. She didn't quite know what that was so she got me a microscope. I didn't want to disappoint my mother, so that got me started into microbiology."

We asked him to take us on a tour of the average home to point out the germiest spot in each room. But before we begin, know that your cellphone is the biggest germ culprit. It's easily the dirtiest thing around you with ten times more germs than a toilet seat. A recent study found there are nearly 17,000 germs on the average high schooler's phone.

Bedroom pillows

Most pillows can be thrown in the washing machine a few times a year to keep them clean. Change your pillowcases once a week to keep germs at bay, Gerba says (Photo: Jack Frog/Shutterstock)

Your pillows are really the only big thing you have to worry about, Gerba says. "People tend to go longer without changing them. Your face is always on it so that means a lot of microorganisms."

The tops of the covers stay pretty clean, he says. Sheets get a little worse because they're covered during the day so it's dark and moist and a breeding ground for germs.

His advice: maybe once-a-week pillowcase washes and no sharing.

Bathroom towels

Can you find the germiest item in this pristine bathroom? Can you find the germiest item in this pristine bathroom? (Photo: Artazum/Shutterstock)

You'd think the most germs would be lurking around the toilet bowl, but it turns out the porcelain throne is one of the cleanest spots in almost anyone's home, says Gerba. People are so afraid of ickiness, they clean the toilet religiously, he says.

"People are terrified of butt-borne diseases, but there aren't any. The most protected thing in the world is your hind end from what I can figure out," he says. "The cleanest area in the home seems to be the top of the toilet seat. If anybody ever dares you to lick a surface in a home, pick the toilet seat." (Just pause for a moment to let that one sink in.)

So where are the germs? That innocuous hand towel.

"What happens is, people wash their hands after they go to the toilet. There's always some bacteria left on their hands, which they wipe on the towel. And the towel stays damp," Gerba explains. "You'd get more fecal bacteria on your face if you wiped your face in a hand towel than if you stuck your face in the toilet."

Because people share hand towels, the germs get spread back and forth. Gerba suggests changing the towels every couple days or using disposable paper ones.

Bathroom faucets are pretty germy, too, he says. When you turn the water on to wash your hands, that contaminates the faucet. When you turn the water off, you recontaminate your hands.

Kitchen sponges

Sink full of dirty dishes The dirtiest item in the kitchen is not the kitchen faucet or those dirty dishes. (Photo: Joseph Thomas Photography/Shutterstock)

"The sponge — or similarly, the dish cloth — is probably the most germ-laden thing in your house," he says.

About 15 percent of kitchen sponges contain bacteria — like salmonella and E. coli — that can make you sick. To stay safe, some experts recommend every few days microwaving the sponge for 30 seconds or wash it in the dishwasher. However, a new study finds that the strongest and stinkiest bacteria might survive the nuking. Instead, you should run it through the washing machine at the hottest setting using detergent and bleach or, better yet, replace it weekly or use it in a less germ-sensitive place, like the bathroom.

The cutting board doesn't get off that easy, though. Gerba's studies show there are 200 times more fecal bacteria on the average cutting board than on the top of the toilet seat.

"You use it for hamburger, rinse it, then use it to make a salad," Gerba says. "So you end up with a salmonella salad before you know it."

To protect yourself, use one cutting board for meat and one for vegetables and wash them after each use in the dishwasher or with a disinfectant. Then there's less of a chance for cross-contamination.

In general, the kitchen can be problematic. "The average adult gets a bad case of diarrhea every other year — one where it's really a gut cruncher — and about 80 percent of foodborne illness likely originate from the home," Gerba points out, making the connection. "It's actually safer to eat out because at least restaurants are inspected."

The couch

Man resting on a couch Your couch cushions may be even dirtier than your remote control. (Photo: Africa Studio/Shutterstock

You may want to think twice before you settle into that comfy couch to watch TV. At least throw the cushions on the floor — and maybe read a book.

"Recent work we are doing indicates that the cushions are the worst, then the carpet and TV remote," Gerba says. "The remote control used to always win. But then we started studying couches and cushions and they seem to be far worse. We're just gathering data now, but it doesn’t look good."

You can't really disinfect pillows and seriously, when was the last time you washed your throw pillows or even your sofa cushions?

And the remote? Well, that's why you shouldn't watch TV in a hotel room. "Nobody ever disinfects or cleans it. When people are sick, they jump in bed with the remote control and all those nasty organisms get in the cracks and crannies."

Family cars

Mom, son in a family vehicle The car your kids ride in most often is the germiest one of all. (Photo: kikovic/Shutterstock

The car-germ connection is interesting, says Gerba. "The worst cars are vans because they usually indicate kids are present. The cleanest is the car that's taken to work because kids typically aren't going in it."

The grossest part of any car is the dashboard because the air flies over the top of it, sending all the organisms with it. After that, germs thrive in the car seat if you have one, then the cup holder and the change holder.

Home office

Father and son in home office When the whole family uses the home office, more germs land there, too. (Photo: Zivica Kerkez/Shutterstock)

Home offices are typically germier than work offices, Gerba says, because people eat more in their home work spaces plus children often will play on the computer and the whole family may use the area.

"We've even found MRSA in home offices, which really surprised us," says Gerba, referring to an infection caused by a type of staph bacteria that is resistant to many antibiotics.

The worst area is the top of the desk. "People usually don't clean it until they stick to it."

After that, it's your phone, mouse and keyboard. Get out some antibacterial wipes and get busy.

Toys

Boy playing with ball outside If he plays with this ball outside, don't bring it into the playroom indoors without washing it. (Photo: Dima Bobko/Shutterstock)

Small children and any toys that go outside are a bad combination. "Outdoor toys roll around in the lawn where dogs poop so they get fecal bacteria all over them."

The thought of teeny tiny children obviously makes Gerba shudder.

"The most germy area I go into is a daycare center. I almost feel like I should wear a hazmat suit. They're pooping, sneezing, you name it."

Editor's note: This story has been updated since it was originally published in March 2015.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.