From taking a shower to brushing your teeth to washing your hands, you practice good personal hygiene on the daily. And it’s not just because you like the way your new shampoo smells, either. You know these habits keep you clean and, in some cases, can even help prevent you from getting sick.
But after all that lathering, rinsing and scrubbing, can you actually be too clean for your own good?
That’s what supporters of the so-called hygiene hypothesis think, saying that the rising rates of allergies, asthma and other autoimmune disorders in children is linked to our increasingly hygienic surroundings. And while statistics appear to back this up, experts in the fields of immunology and infectious disease say, not so fast.
“To say that being clean means you’re at a higher risk of allergies or asthma is not quite right,” agrees Dr. John Lynch, an associate microbiology professor at the University of Washington School of Medicine and medical director of Harborview Medical Center’s Infection Control, Antibiotic Stewardship and Employee Health programs.
The problem, he says, is that the hygiene hypothesis doesn’t tell the full story.
What is the hygiene hypothesis?
Largely popularized by British epidemiologist David Strachan in 1989, the hygiene hypothesis theorizes that because modern parents are able to clean their children and households more effectively, kids these days just aren’t exposed to the same level of germs as previous generations.
That excessively sterile upbringing — hand sanitizer, anyone? — means children’s immune systems aren’t able to develop properly and, as a result, malfunction.
When you look at the statistics, they seem to support this idea. In developed countries, the number of kids who have asthma and allergies has been going up.
Washington state has some of the highest incidences of asthma in the nation, and it’s only increasing. More than 600,000 Washingtonians have asthma, and nearly 120,000 of them are children.
Research from the Centers for Disease Control and Prevention shows that the same trend applies to kids who have food allergies. Now 1 in 13 children in the United States has a food allergy, a 50% increase between 1997 and 2011. To put it in perspective, that means in every American classroom, there are two kids who may have a food-related allergic reaction.
Is the hygiene hypothesis true?
Don’t toss out your hand soap or quit bathing your kids just yet. Remember, while data appears to back up the hygiene hypothesis, it’s not a complete picture.
“There was no randomized control study to determine the hygiene hypothesis,” Lynch explains. “It ends up being observations of populations, biased by our ability to detect diseases. You have less likelihood of being diagnosed with asthma or even diabetes in a developing country versus a developed country.”
What Lynch means is that as the field of medicine has advanced in recent decades, so has our ability to detect and diagnose conditions like the aforementioned food allergies and asthma. And the reason why much of the evidence to support the hygiene hypothesis comes from industrialized countries is because these nations have greater medical infrastructure and resources to detect autoimmune dysfunctions than the developing world.
So while the number of children with asthma and food allergies is higher than in decades past, there’s no way to know if that’s because more kids actually have those conditions or if it’s because doctors are more able to recognize and diagnose those conditions.
Another problem with the hygiene hypothesis, Lynch notes, is that while getting exposed to some germs does help build up your immune systems, other types of bacteria and viruses can actually cause asthma or serious diseases.
That’s why researchers and medical professionals in Lynch’s field of infectious disease and immunology cringe at the name “hygiene hypothesis,” he says. It implies that good personal hygiene is related to higher rates of disease when, in fact, it’s the opposite.
Think about it this way: If the hygiene hypothesis is really accurate and being overly clean makes our immune systems malfunction, children who don’t wash their hands, are exposed to pathogens on a regular basis and live in unclean conditions would be the healthiest.
“Unfortunately, we know that people who live in places that lack access to hygiene die more frequently,” Lynch says.
How do you build up a child’s immune system?
It’s not that the hygiene hypothesis gets it all wrong. Children do need to be exposed to certain microorganisms in order to influence the right immune response and develop a robust immune system. And having a too-clean environment can hinder that in some ways.
“We don’t need to sterilize things with antibacterial products or create an incredibly hygienic environment,” Lynch says. “You don’t want to put any extra chemicals or agents in anything because that’s how you create antibiotic-resistant bacteria.”
In fact, your body is full of trillions of bacteria, fungi and viruses — an entire community called your microbiota — which are critical to your immune response and overall health.
Now here’s where glimmers of the hygiene hypothesis come in: Children develop a healthy microbiota by acquiring bacteria in a variety of ways, from vaginal birth and breastfeeding to getting kissed by their parents and sticking their fingers in their mouths as babies.
“That’s all normal,” Lynch says. “We don’t want women washing their breasts before breastfeeding or parents washing their lips before kissing their children.”
What also matters for immune development, though, is what you’re exposed to and how that affects your body. Getting a common cold virus is a totally normal part of childhood. But being exposed to an antibiotic-resistant superbug is a much more serious issue.
“When you’re talking about the hygiene hypothesis, the point of contention is that the focus should be less about hygiene and more about access to the right microbiota,” Lynch explains.
What’s the takeaway from the hygiene hypothesis controversy?
So while the hygiene hypothesis isn’t totally correct, going in the opposite direction to an overly sterilized childhood isn’t exactly healthy either. It can feel like the balance between exposing children to good bacteria and keeping them safe from the bad stuff is pretty much out of your control.
Just try to keep everything in perspective, Lynch says. Use common sense — and maybe go easy on the hand sanitizer.
“I like to think of it like this: Hand washing is important if you’re around someone who’s sick or if your kid is rolling around on the floor at a restaurant, but maybe not so much if they’re just playing outside at the park,” he says.