Where Are We Now?
Food allergy is a growing worldwide epidemic that adversely effects up to 10% of the population. Causes and risk factors remain unclear and diagnostic methods are imprecise. There is currently no accepted treatment for food allergy. Therefore, there is an imminent need for greater understanding of food allergies, revised diagnostics and development of safe, effective therapies. Oral immunotherapy provides a particularly promising avenue, but is still highly experimental and not ready for clinical use.
IgE-mediated food allergy (FA) is a growing problem worldwide. Defined as an immune response to a given food that occurs reproducibly upon exposure, FA affects anywhere from 1 to 10% of the population, with greater prevalence in children (4–6% in the USA vs ~2% in adults). This prevalence has been increasing at a rapid rate, as has been demonstrated by data from the USA, UK, Australia and China.
Despite this burden, the only currently accepted treatment for FA is complete avoidance of the offending allergen, with epinephrine delivered in the case of accidental ingestions – which occur frequently, even in the most careful patients, and are often undertreated. As such, FA is a highly stressful condition, generating elevated anxiety in allergic subjects and their families. FA is associated with significantly decreased quality-of-life scores to a degree that is greater than that seen in many other chronic childhood diseases. There is, therefore, an urgent need for an effective therapy for the treatment of FA. Contingent with this is the need for greater understanding of the mechanisms of FA, as well as a need for more precise diagnostics. There is still much that remains unknown, and extensive research in many areas is needed to fully understand this disease and potential treatments. This article aims to address the current state of the field and to speculate on its future.
Acute symptoms include urticaria, flushing, angioedema, abdominal pain, nausea, vomiting, diarrhea, wheezing, coughing and/or bronchospasm, rhinorrhea and hypotension or syncope.
Not all foods are allergenic; in fact, of the over 12,000 food allergens known, only a small number induce allergies. Further questions are raised by spontaneous resolution of FAs. Children usually outgrow allergies to milk, egg, soy and wheat, but not peanut or tree nut allergies.Why this happens, and why only some FAs resolve independently while others remain, is unclear
The environment of the gut is also likely to be crucial. Intestinal permeability is positively associated with increased FA incidence; a study of food-allergic infants demonstrated they had greater intestinal permeability compared with healthy infants, an effect that lasted even after 6 months on an exclusion diet. Likely to be even more important are the microbiota found in the gut. The hygiene hypothesis suggests that changes in the pattern of intestinal colonization during infancy and decreased exposure to infectious agents in childhood are important factors in the development of allergic disease, and may help explain why allergy prevalence is increasing. Antibiotic use and exposure to pets, farms and farm animals have been linked to decreased atopy risk. In addition, differences have been found in gut microbial flora between allergic and nonallergic children, suggesting certain microbes may be more important to sensitization than others.