A recent comparative study into the lives of wild and laboratory rodents seems to throw light on the aspect of building stronger immune systems when exposed to germs in the environment, rather than protecting against it.
A team of researchers from Duke University analyzed the immune systems of mice and rats which live in laboratories with those which live in the wild.
Senior researcher William Parker said, "Laboratory rodents live in a virtually germ- and parasite-free environment, and they receive extensive medical care -- conditions that are comparable to what humans living in Westernized, hygienic societies experience. On the other hand, rodents living in the wild are exposed to a wide variety of microbes and parasites, much like humans living in societies without modern health care, and where hygiene is harder to maintain."
Drawing a parallel with the lives of humans, scientists imagine that people in hygienic environs who are not exposed to germs have less immunity against allergies and diseases. Further studies are required to conclusively prove this hypothesis.