We’re just beginning to learn the effects our microbiome has on us, but it’s clear that they can be profound. Certain species help digest food and synthesize vitamins; others guide the immune system. Medical researchers have linked obesity, heart disease, and anxiety to properties of the microbiome. In many cases, it’s not the individual species that seem to matter but the richness of the ecosystem. Just as the health of a forest depends upon diversity, our own health appears to benefit from the presence of a wide range of uninvited guests, many of which coevolved with us.
There’s a growing body of research showing that children exposed to lots of germs early in life are less likely to develop allergies, asthma or autoimmune disorders as they grow up.
But now there’s a new twist on the theory, known as the hygiene hypothesis in scientific circles, and it’s about little girls in cute little dresses.