Food allergies affect up to 6% of young children and 3%–4% of adults. They encompass a range of disorders that may be IgE and/or non-IgE mediated, including anaphylaxis, pollen food syndrome, food-protein–induced enterocolitis syndrome, food-induced proctocolitis, eosinophilic gastroenteropathies, and atopic dermatitis. Many complex host factors and properties of foods are involved in the development of food allergy.
The first case of oral immunotherapy (OIT) to treat food allergy reported in Lancet in 1908 offers an accurate description of an episode of severe anaphylaxis on exposure of a child to egg. The demonstration that large amounts of egg can be tolerated after gradual desensitization followed by long-term maintenance with continued consumption of egg raises the question of how long oral immunotherapy needs to continue. These issues are more pertinent than ever, with a growing number of publications and research into immunotherapy for food allergy.
Early studies of subcutaneous immunotherapy to peanut were discontinued because of the high rate of anaphylactic reactions. More recently, studies using oral immunotherapy or sublingual immunotherapy to peanut, milk, and egg have shown promise. Recently, a first safety trial has been performed with a hypoallergenic mutant of fish parvalbumin in subcutaneous immunotherapy for the treatment of fish allergy.
Oral immunotherapy using raw or heat-modified food appears to be more effective than sublingual immunotherapy. A high proportion of patients were able to pass an oral food challenge after 1 to 4 years of oral immunotherapy with a 20- to 100-fold increase in threshold reactivity and daily ingestion of high maintenance doses (300-4000 mg) of the food protein. However, the rate of SRs requiring epinephrine, which were observed in up to 25% of participants, especially those using raw food, is still too high for recommending oral immunotherapy in daily practice. With sublingual immunotherapy, the doses are much lower (<10 mg/d), and the safety profile is better, but the threshold of reactivity reached at the end of the treatment is usually lower, affecting efficacy. Although increased food-specific IgG levels and decrease in basophil activation are observed during immunotherapy, there are currently no biomarkers to predict the response. Efficacy can only be demonstrated through sequential oral food challenges. A good response is associated with a longer allergen immunotherapy duration and a larger amount of food tolerated. Associated treatments, such as omalizumab, can reduce adverse reactions and improve efficacy.
Because of the risk of adverse reactions, including anaphylaxis, EAACI guidelines do not recommend food allergy immunotheray for routine clinical use (level III, grade D). The procedure should be performed only in highly specialized centers with expert staff and adequate equipment and in accordance with clinical protocols approved by local ethics committees.
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Wang J et al. Food allergy: recent advances in pathophysiology and treatment[J]. Allergy, asthma & immunology research, 2009, 1(1): 19-29.