Antimicrobial soap, hand sanitizer, household disinfectants -- is it possible to be too clean? A growing number of experts say yes.
Allergies and asthma are on the rise, and many doctors believe it is linked to the way many of today's parents are raising their children -- in a world where every germ is the enemy.
"We're designed when we're born to get this exposure, and we've been removing that," said Christine Cole Johnson, Ph.D.
Cole Johnson is a Henry Ford Hospital researcher who has studied the impact having a pet can have on a family's risk of developing allergies and asthma.
Joanne Gutowsky of Novi and her daughter Katherine were part of that research. Katherine is 9 now. She was enrolled in the study not long after she was born.
"I had a lot of people telling me, 'Don't get a dog. Don't let the dog by the kids. Don't let the dog lick their faces, don't let 'em lick their hands,'" said Gutowsky.
But her instinct as a mother was different, starting with her first born and continuing with all four of her kids.
"Josh was a few months old, and we specifically put the dog and the baby next to each other," said Gutowsky.
Cole Johnson and her research team was one of the first to challenge conventional wisdom about pets and allergies.
"Most doctors would tell patients not to have pets in the house if they didn't want the child to be allergic, but it was the opposite," said Cole Johnson.
It was another piece of the evidence for something that has been called the "hygiene hypothesis." The central idea is that it is possible to be too clean.
"The immune system is not learning appropriately how to handle those exposures and not as good at distinguishing what's good and what's bad," said Cole Johnson.
Without this immune system education, the body begins to react inappropriately to common things in the environment -- hence allergies.
"Having pets in the house, cats, dogs, seemed to protect children against allergies," said Cole Johnson. "Not just allergies to the animals, but allergies to ragweed and pollen and everything."
Results aren't guaranteed. Katherine who was exposed regularly to the family dogs, Mozart and Daisy, does have seasonal allergies, but none of the children have allergies to foods or animals.
Now, the theory is being tested more specifically.
"We're thinking it's something about what pets bring into the house probably, not sure what that is, but it may be soil microbes since they come in and out. It seems like dogs had a stronger protection than cats," said Cole Johnson.
That's because dogs travel outside more. Cole Johnson believes it's not the fur or dander; it's the bacteria and microbes in the gut that are critical.
"It seems that the first year of life and maybe even the first six months and maybe even prenatally are all very important," said Cole Johnson.
This isn't saying routine hygiene isn't important.
"If you're trying to prevent flu and things like that and viruses that are seasonal, you need to wash your hands," said Cole Johnson. "Just like in nature, a balance is important. I do think that babies and kids in school should play and be allowed to get dirty and go outside a lot."
Henry Ford Hospital is continuing to research the interplay between pet exposure and immune diseases like asthma and allergies. They are currently enrolling in a couple of different studies, one specifically, in partnership with the Michigan Humane Society is recruiting both families getting a dog for their home, and families with no pets in their home.
To learn more about how to be a part of the study, click here.