I am not a fan of the 3-second rule.
If food falls on the floor, it’s dirty. It doesn’t matter whether it lies there 3 seconds or a fraction of a second. The instant food touches a dirty surface, it’s a goner. Into the trash bin it goes.
But that’s just me.
The kids I know are HUGE fans of the 3-second rule.
Or, rather, the no-second rule. Food is just as delicious whether it’s on the floor or on their plate. Why shouldn’t they be able to eat a candy that fell through the cracks in the sofa and has been nestled there among the dust bunnies for the past year?
Kids find it easier to believe in Santa Claus than germs. After all, Santa Claus is real—those Christmas-morning presents prove it—while no can see a germ. “Germs” is just a word parents invoke to keep kids from doing fun things.
One of the biggest lessons we teach our kids is what is dirty and what is clean.
Clothes you put on this morning are clean. Clothes you took off last night are dirty.
Dishes in the cupboard are clean. Dishes in the sink are dirty.
Freshly-washed hands are clean. Any other time, they’re dirty.
History proves the magnitude of this lesson. Proper sanitation saves lives. It prevents life-threatening illnesses, chronic diarrhea, parasites, you name it.
Even today, 1.2 million children around the world die of diarrhea and related diseases each year, often as a result of poor sanitation. The Rehydration Project tells us that “diarrhea is the second leading killer of children around the world.” 
So your kids had better well wash their hands!
But in the West, life isn’t as dirty as it is elsewhere.
People use toilets. Farm animals are kept out of the streets. You can drink tap water.
American kids aren’t dying in huge numbers from poor sanitation.
Instead, they’re suffering from something extraordinarily counterintuitive:
A lack of bacteria.
Case in point. When’s the last time your kid made a mud pie?
When I asked myself this question, I was shocked by the answer.
Despite living in the countryside, my daughter has never played in the mud. She’s jumped in muddy puddles, for sure. But mud doesn’t entice her in the same way as, say, her tablet.
Most parents today know that a little dirt is good for their kids.
We know this thanks to a British epidemiologist, who proposed back in 1989 that dirty living conditions actually help protect against allergies and asthma.
The hygiene hypothesis argues that our kids are too clean. They’re not exposed to enough germs at a young age. We want their immune system to be fighting off viruses and bacteria, because then it will be too busy to react to allergens.
Researchers point to farm kids as evidence. Children raised with exposure to farm animals develop fewer allergies.
As a farm kid myself, I can attest to this. I thought allergies were a “town kid” disease. I felt so sorry for my friends with hay fever, who sneezed their way through the spring blossoms and showed off nasty-looking rashes from sitting bare-legged on the grass. I’d stay indoors if that happened to me, too.
But the hygiene hypothesis has come under attack in recent years.
Scientists no longer believe that it can explain the steep rise in asthma over the past decade.
Instead, they argue that we should be focusing on the microbiome, defined as the “10-100 trillion symbiotic microbial cells harbored by each person, primarily bacteria in the gut.” 
You’ve heard about the microbiome before. It’s the focus of functional medicine, as well as all those probiotics manufacturers, who want you to spend your hard-earned cash on replenishing the good bacteria in your gut.
Our modern lifestyle has impacted the microbiome to such an extent that our immune response has been compromised.
So it’s not that kids need more dirt in their lives.
It’s that they need more microbes.
And not just any microbes…
But rather the microbes that have been in our environment since the dawn of time.
These microbes even have a nickname: “Old Friends.”
They’re the harmless microbes that come from living among other people and being outdoors in nature. 
Children first meet these Old Friends in the womb. A natural birth, as opposed to a C-section, protects against allergies. Breastfeeding transfers even more microbes, giving children who’ve been exclusively breastfed for the first 6 months protection against asthma. 
Being raised in a large family also helps. If you want a small family, though, day care provides the same advantage.
Surprisingly, even diet and antibiotic use have a strong effect on a child’s risk of developing allergies.
If a mother has to take antibiotics during pregnancy, her child has a higher risk of allergies. Children should given antibiotics as a last resort.
An anti-allergy diet supports a diverse microbiome. Children should eat a wide range of different foods, including fish and an abundance of plant fiber.
So helping your child build a strong immune system is about much more than letting your child get dirty.
It’s about supporting her microbiome from the day you learn she’s inside you.
Make sure your child gets outside and plays in the mud and grass. Take him to petting zoos. Encourage her to play outdoor sports, like soccer or baseball. Get a dog.
And start it young.
The sooner your child is exposed to these Old Friends who will help train her immune system, the better.
There’s nothing more heartbreaking than watching a child suffer through asthma attacks or sniffle through a beautiful spring.
It’s up to us as parents to do what we can to help.
Will letting your kid eat food off the floor or catch the neighbor kid’s cold help boost his immunity?
But wrestling with a puppy will help—and it’s much more fun than that linty candy stuck in the sofa. 😉