We went to the man known as the Germ Doctor to get the answer, an answer that shocked Tucsonan Alix Oglesby, a self-admitted germaphobe.
She says, "I don't like dirt. I don't like germs."
But it turns out, one of her weapons in the battle against her arch enemy could turn on her and her family.
University of Arizona germ expert Dr. Charles Gerba found out what makes vile vacuums.
Gerba says, "What we find out that bacteria like salmonella and e coli will actually grow inside a vacuum once they're sucked up into the vacuum."
You heard right.
They don't just hang out. They grow. Multiply.
Your vacuum can become a breeding bag for bacteria.
Gerba says, "So we think what's happening is you're taking the bacteria that are probably starving in your carpeting and bringing them right to the brushes where food is accumulating or inside of the vacuum cleaner bag. Basically what's happening is your vacuum cleaner is becoming a meal on wheels for the bacteria."
And for cold and flu viruses too.
Gerba says, "We also found in looking at brushes in vacuum cleaners that about half them had E. coli and other fecal bacteria."
Alix says, "No, I would never think that would be in my vacuum cleaner."
She says, "Usually, I'll start with the tile and I'll do all the tile and then carpets, then I'll go into the bedrooms and do the carpets in there."
Exactly what Gerba would recommend because, it turns out, not only are all those germs enjoying a smorgasbord. They're also catching a free ride.
Gerba says, "Basically, you're picking up germs from one part of your house and dropping them off at another. Always vacuum those areas first which are the cleanest and then go to the dirtier areas so you're not moving germs from one location to another in the home."
And what about the vacuum itself.
Which was better in this study, the kind that uses a bag, or the bagless type?
Gerba say, "I think the best thing with vacuum is to use a bag-type vacuum cleaner, one that has a sanitary seal so when you lift it out, it seals it and you can just throw it away."
As for bagless vacuums, Gerba says, "We actually found out the bacteria will cling to the insides of the receptacle."
And Gerba says empty your vacuum or change the bag outside because "you get a cloud of E. coli or salmonella that may have been growing in your bag."
As it happens, Alix does everything right.
She even empties her vacuum out in the garage.
Now, if you have a bagless vacuum cleaner, what do you do?
Gerba recommends you put on gloves and clean the receptacle with diluted bleach or disinfectant, and just let it air dry.