Howard Hughes, the mid-twentieth century American businessman, went from billionaire playboy to world-famous recluse and obsessive-compulsive germaphobe. He believed his neighbors made him sick by living unkempt lives, demanded that anyone who touched his food use layers of paper towels (and that most of that food was contaminated anyway), and yet still believed that everything was covered with a small layer of dirt that no amount of cleaning would help.

I think all of us who lived through the global pandemic may have some understanding of Hughes’s need to socially distance from others, and stories of bacteria leading to food poisoning should make us all be conscious of safely handling our food.

But the dirt part is harder to get my head around. If I saw one of my children eating dirt, playing in the cat box, or wrestling with the dog, I was sorry for whoever was doing laundry but took comfort in the fact that they might be arranging their adaptive immune system to respond to horrid infections later in life.

Robust collections of healthy bacteria in a child’s bowel can build immunity at a young age that lasts through a lifetime. In other words, children who eat dirt, pick their noses and eat the snot, and luxuriate in covering themselves in mud, might have healthier immune systems because they do that.

As counterintuitive as all that sounds, studies of rural children who wallow and even swallow dirt when they are little reveal that they are less prone to allergies that affect suburban and urban children.

Children living on a farm, being around and breathing in (and likely ingesting a bit of) manure have less allergies and healthier immune systems. There is also evidence in adults of being “dirt happy,” meaning playing in and laying in dirt acts as a natural antidepressant and mood lifter.

This is something we continue to study but think about that the next time you resist the urge to lie on the ground.

Howard Hughes be damned — the power of dirt might be the best thing for training immune systems. There is growing evidence that this power of dirt starts the moment we are born.

This is called the “Hygiene Hypothesis.”