It seems that I am not alone here to think that the hygiene hypothesis has thrown back allergy research for 20 years – despite the desperate attempts of journalists and scientists. Here is an an excerpt of Hygiene hypothesis: wanted—dead or alive
When it comes down to all, the best evidence to prove or dispute the hygiene hypothesis will probably come from ongoing and future randomized trials of interventions, e.g. treatment with probiotics and microbial products, that have been developed in the light of the hygiene hypothesis. In the mean time, we must prepare ourselves to face the results of these trials as well as of other types of evidence. It is a possibility that it may turn out that the hygiene hypothesis is more dead than alive, or at the least needs another revision.