To see rats healthy you need to provide it with dirty environments like that of the sewers and farms. Two studies reveal that the mice that live in sewers and farms seem to have healthier immune systems, compared to their squeaky clean cousins that thrive in healthy and antiseptic regions.
This finding clearly can blame the sanitized Western world environment partly for the increasing rates of allergy and asthma cases in human, along with some autoimmune diseases — like Type I diabetes and rheumatoid arthritis.
This theory is called the hygiene hypothesis. It reveals that disease and dirt early in life do not challenge the immune systems of men, which lead the body’s natural defenses overreact to small irritants such as pollen.
Via: Live Science