We have a problem: We’re just too clean! The rise in allergies and autoimmune diseases during the past few decades may be at least partly due to our lack of exposure to the microorganisms in dirt.
We once walked barefoot in the dirt and washed it off of our food. Now we wear shoes and buy pre-washed vegetables from the grocery store, covered in plastic wrap. Even the increase in the rate of Caesarean section births means a potential loss of the germs that are usually passed from one generation to the next. The microorganisms in dirt establish "normal" background levels that keep our bodies from overreacting to germs.