Wonderful condo you got us Ian, third floor ocean front, directly over the pools!
Whether you like him or not, it's wise to be nice to Ian!
As you can tell from reading the article, the hygiene hypothesis concerns more than just the parasites I mention so often. The modern hygiene hypothesis is more about the loss of "evolutionary normal" conditions in the last 100 years or so, whatever that may encompass.
I think it's interesting that one of the mainstays of the hygiene hypothesis has been that proper exposure to "evolutionary normal" conditions through puberty might send someone into adulthood with an educated...mature, immune system better able to correctly handle future assaults.
Some of the most long held and perplexing questions involving MS incidence involve the disparity of odds of adults vs adolescents migrating from low to high/high to low MS incidence areas.
This area of the hygiene hypothesis seem to make those answers evident ie.. someone reaching adulthood in a low MS incidence area who migrates to a high MS incidence area would continue to enjoy low incidence, whereas someone migrating from a low MS incidence area to a higher MS incidence area before puberty would expect the higher incidence of the area he/she is migrating to.
To large degree the opposite migration would also hold true to the noticed statistics. Since no one from the higher MS incidence areas are realizing "mature" immune systems, when moving to a lower MS incidence area, for the most part regardless of adolescent or adult, they would continue the higher MS incidence rates because even though they are moving to a less "hygiene" area, they likely are going to continue living under the "developed" conditions they are accustomed to.