New studies further question the hygiene hypothesis of allergy induction. One study shows that a household bacterial elimination strategy does not lead to more — it even leads to less asthma.

Children living in a house regularly cleaned with bleach were less likely to have asthma (OR, 0.10; CI, 0.02–0.51), eczema (OR, 0.22; CI, 0.06–0.79) and of being sensitized to indoor aeroallergens (OR, 0.53; CI, 0.27–1.02)

Another study, by designing a 16S rRNA chip, examined a snapshot of urban air in San Antonio — the aerosol harbored at least 1,800 diverse bacterial types

a richness approaching that of some soil bacterial communities

You probably know the joke that before taking a deep breath think where the air has been before…

Addendum

The ecology of human skin has now been also reported – highly diverse, well conserved but low-level interpersonal consensus: scienceblog:doi:10.1073/pnas.0607077104