We have been learning more and more about the importance of the gut microbiome, from emotions and intelligence to immune responses and hormones. It is my opinion that children should be allowed to explore and "get dirty" so to speak. It would train and expose their body to different elements and pathogens that build a balance and "natural" microflora. By babying and obsessed with keeping kids clean and spotless all the time, we may actually hurt them more in the long run.

A bit of dirt, some sneezes, a scratched knee, a few bruises, all of them are normal and expected. Kids should be allowed to have those, otherwise we might deprive them of a healthy life later on.

Anecdotally, I grew up in a not so clean place. Thinking back, I am surprised it was so normal back then with how unhygienic everything was by Western standards. You would think people living in that kind of environment would be sick and disease ridden all the time. Yet it was the opposite. Allergies were practically unheard of and stuff like a cold or flu were almost never severe enough to send anyone to the hospital. Basically, people I knew back then were a lot more robust and had less health concerns than most of my coworkers and neighbors nowadays despite a world of differences in hygiene standards.

IIRC, germ free rodents grown to be absolutely sterile for specific medical tests are extremely sick all the time and are so weak you would not believe they are genetically the same with those rats thriving in the sewer. I guess it is for the same reason.