Once upon a time, my immune system was an omnipotent being, capable of tackling any illness with rapid efficiency. Like a lean and wiry hound dog it would locate the infection with speed and agility, and then the mighty White Blood Cell Hunters would move in and obliterate the prey before it could do any damage at all.
But alas, as I made the subtle transition into late teens, this behemoth wall I’d built against the dangerous organisms of the world began to deteriorate.
I think I know why.

This isn’t us. These are somebody else’s kids. (I Googled “kids mud gross” and found this picture.) But this is exactly what we used to do, in a mud pit that formed in a bend of the Illinois river. This same river happens to be an industrial river; barges are frequently traveling up and down carrying cargo such as gasoline, sand, coal, gravel, something that looked like piles of rice, etc. And since the water is slowing down and eddying in this particular bend, it deposits all the fun pollution in this giant marsh that, when you jump off a certain log, you can sink up to your belly button in.
It was only the coolest thing. Ever.
Fact: I am alive, sitting here, waiting for my hair to dry, and so far I haven’t grown any extra toes or anything.
Conclusion: I survived the Mud Pit. My immune system was still Godlike at the time.
Fact: Eventually, our parents made us stop playing in the mud, and even took steps to prevent us from sneaking away from them to go do it anyway, like we did for a while afterwards.
Conclusion: This is what happened to my immune system. Suddenly, we actually started to spend sick days in bed moaning, aghast at the reality of Strep or the Stomach Flu.
This was a difficult time for me.
Face it- kids are tough. I made a small fortune babysitting in middle school, and I watched kids eat candy found on the ground, share popsicles with the dog, lick their fingers after numerous outdoor activities, forget to wash their hands, refuse to brush their teeth, you name it. (How I made a fortune if I couldn’t prevent such things, I don’t know.) If we listen to Darwin, more than half of us don’t deserve to live to pass on our genes.
But as you can see from my example above, it’s just preparatory conditioning. The common school of thought is that kids are tough because their unsanitary natures call for it. On the contrary- they’re tough because their unsanitary natures make them that way. If kids actually listened to the countless warnings and carefully disinfected themselves after every excursion into the wide world, their superior immune system would disintegrate from lack of use. A scrape on the knee would become fatal; a kiss from Mans Best Friend would become a childhood destroyer.
There is a lesson to be learned from all this. A little dirt has to come with health, Yin and Yang style. A bit of the bad is needed to make the good, being small has to come before being big. The invincible has to be in a constant state of vulnerability. Even little kids know this.
Why is it so hard for us elderly folk?