Immune basis of food allergic reactions.

Food allergies are diseases where the normal tolerance response to oral antigens is altered. Recent advances have begun to uncover mechanisms that mediate sensitization to food allergens and maintenance of this disease. Production of alarmins by epithelial cells triggers a cascade that leads to allergen-specific IgE synthesis. A role of IL-9 in mast cell recruitment and amplification of allergic response has also been identified. In recent years, increasing evidence suggests that sensitization to food allergens can be developed by non-oral routes, in particular the skin, which led to the proposal of the 'dual exposure hypothesis'. Environmental factors such as diet or microbiota can shape the immune system to promote tolerance or sensitization to food antigens. While the mechanism of primary tolerance to food antigens is quite clear, the one leading to permanent tolerance in already food-allergic individuals through immunotherapy is still under study. Understanding the mechanisms by which oral tolerance is suppressed and sensitization is developed will help to identify new targets to develop combinatory therapies for the treatment of food allergies.