Babies are constantly putting things in their mouthes. In classes for raising newborns, nurses and teachers always talk about checking your floors to make sure there is nothing that the child can fit into their mouth and choke on. Choking is a big concern, but some parents also are determined to raise their kids in an ultraclean environment. By not allowing children to get a little dirty, these parents might be preventing them from developing their immune systems to respond to allergies, asthma, and other autoimmune diseases.

“What a child is doing when he puts things in his mouth is allowing his immune response to explore his environment,” writes Mary Ruebush, a microbiology and immunology instructor, in her new book, “Why Dirt is Good”. “Not only does this allow for ‘practice’ of immune responses, which will be necessary for protection, but it also plays a critical role in teaching the immature immune response what is best ignored.”

In this article in the New York Times, writer Jane Brody talks about some of the advantages that a little dirt can have for children. She also examines a couple of different scientific studies that are looking at dirt’s benefits to our immune systems. Her conventional wisdom seems to be that washing with soap is still pretty good, but you also can let children run around outside barefoot. You might be helping their immune system in the long run.