The hygiene hypothesis is the most common theory for increased food allergy. It begins with a lack of early childhood exposure to infections. Without proper stimuli the immune system does not receive necessary education. When presented with food proteins, the normal response (tolerance) is replaced by hypersensitivity.
A recent article, in the early edition of Proceedings of the National Academy of Science*, adds further support for a revised hygiene hypothesis, with emphasis on symbiotic microorganisms living in the gastrointestinal tract. The authors identified a common bacteria found in the gut (aka probiotic) that may prevent development of food allergy, specifically peanut. Much research is needed but here is another potential pathway to a cure for peanut allergy.
* Commensal bacteria protect against food allergen sensitization; Stefka et al.