Does exposure to germs in toddlers strengthen the immune system?

Toddlers and dirt: There is a good chance that exposure to germs, both bacteria and certain common viruses, dirt, as in growing on a farm and catching infections from older siblings reduces the development of allergies. This is called the "hygiene hypothesis" - that living in too clean an environment leads to more allergies.

Yes: Exposure to germs in our everyday world will make the immune system stronger.