Daily administration of small, incremental amounts of egg protein for treatment of egg allergy

Until recently, the only practical option for people with food allergies was a strict avoidance of allergen-containing food. It is difficult to avoid egg because it is found in many foods. Even with avoidance, the fear of accidental ingestion from mislabelled foods or cross-contamination is an ever-present fear for even the most careful of food-allergic individuals. Accidental consumption of egg-containing foods might cause a life-threatening event. Although there are only a small number of published studies, there is a new type of treatment for egg allergy called 'oral immunotherapy' (also known as 'oral desensitization' or 'vaccination'). This is comprised of daily consumption of a small amount of egg protein, which is gradually increased over time until a full serving is reached. This method could alter the allergic response to the egg protein by the body’s immune system, increasing the amount of egg that can be eaten without inducing an adverse reaction.

We identified randomized controlled trials that compared oral immunotherapy to a placebo or avoidance diet in people with egg allergy. A total of 167 children (100 in the oral immunotherapy group and 67 in the control group) who were aged 4 to 15 years were studied. The evidence to date showed that oral immunotherapy for egg allergy might help a majority of egg allergic children to tolerate a partial serving of egg, as long as they continued to consume a daily amount of egg protein. Side effects were frequent during the oral immunotherapy but they were usually mild to moderate. Nevertheless, five of 100 patients treated with oral immunotherapy for egg allergy required epinephrine administration because of a serious hypersensitivity reaction. Of note, the trials involved small numbers and there were problems with the way they were done, therefore further research is needed.

Authors' conclusions: 

The studies were small and the quality of evidence was low. Current evidence suggests that OIT can desensitize a large number of egg-allergic patients, although it remains unknown whether long-term tolerance develops. A major difficulty of OIT is the frequency of AEs, though these are usually mild and self-limiting. The use of epinephrine while on OIT seems infrequent. There are no standardized protocols for OIT and guidelines would be required prior to incorporating desensitization into clinical practice.

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Background: 

Clinical egg allergy is a common food allergy. Current management relies upon strict allergen avoidance. Oral immunotherapy (OIT) might be an optional treatment, through desensitization to egg allergen.

Objectives: 

We aimed to assess the successful desensitization and development of tolerance to egg protein and the safety of egg oral and sublingual immunotherapy in children and adults with immunoglobulin E (IgE)-mediated egg allergy as compared to a placebo treatment or an avoidance strategy.

Search strategy: 

We searched 13 databases for journal articles, conference proceedings, theses and unpublished trials using a combination of subject headings and text words (the last search was on 5 December 2013).

Selection criteria: 

Randomized controlled trials (RCTs) were included. All age groups with clinical egg allergy were to be included.

Data collection and analysis: 

We retrieved 83 studies from the electronic searches. We selected studies, extracted data and assessed the methodological quality. We attempted to contact the study investigators to obtain the unpublished data, wherever possible. We used the I² statistic to assess statistical heterogeneity. We estimated a pooled risk ratio (RR) with 95% confidence interval (CI) for each outcome using a Mantel-Haenzel fixed-effect model if statistical heterogeneity was low (I² value less than 50%).

Main results: 

We included four RCTs with a total of 167 recruited individuals (OIT 100; control 67 participants), all of whom were children (aged four to 15 years). One study used a placebo and three studies used an avoidance diet as the control. Each study used a different OIT protocol. Thirty nine per cent of OIT participants were able to tolerate a full serving of egg compared to 11.9% of the controls (RR 3.39, 95% CI 1.74 to 6.62). Forty per cent of OIT participants could ingest a partial serving of egg (1 g to 7.5 g; RR 5.73, 95% CI 3.13 to 10.50). Sixty nine per cent of the participants presented with mild-to-severe adverse effects (AEs) during OIT (RR 6.06, 95% CI 3.11 to 11.83). Five of the 100 participants receiving OIT required epinephrine. We cannot comment on whether over- or under-reporting of AEs was a concern based on the available data. Overall there was inconsistent methodological rigour in the trials.

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