Is cleanliness to blame for increasing allergies?

You only develop strong muscles and bones if you put some stress on them in the form of exercise. Without that stress demonstrating the inadequacy of the existing systems our efficient bodies don't waste energy building muscle and bone.

It stands to reason that the other systems of the body similarly only develop when they are required. They need some level of stress put on them to develop to their capacity.

On a related note: using hookworms to "cure" oneself of asthma or hayfever:

http://www.kuro5hin.org/story/2006/4/30/91945/8971

There are some researches going on, which say that intestine parasites decrease sensitivity to allergy. I am quite allergic, but I dont think nonetheless, that I like the idea of having "tenants". BTW, allergy has increased recently, but so did life expectancy [and it especially high in clean countries]....Blame cleanliness?