Risk Management in Case of Egg Allergy

Egg allergies can usually be confirmed by the combination of medical history, prick test, and specific IgE. Prick test with native hen’s egg is more sensitive that with commercial egg extracts [4, 5]. It must be kept in mind that different assays for specific IgE provide variable, not uniformous results considering the absolute values. In case of follow-up to verify immune tolerance development, the same assay should be used [6]. Abstract


Introduction
Food allergies are reported by our patients with increasing frequency.Diagnostics and care for foood allergic patients reperesent a significant percentage of workload in the allergy clinic.Here, we will focus on egg-related allergies.
Hen eggs (Domus domesticus) are an important protein source for human nutrition.Eggs and egg components are part of various foods like mayonnaise, pasta, pastries, sausages, glazes, salads, convenience food, and confectionary.
Egg allergies are predominantly seen during the first years of live.Up to 2% of children and adolescents are affected [1][2][3][4].Hen's eggs and cow milk are the most important food allergens in childhood [2,3].Due to tolerance induction with increasing age, the percentage of hen's egg allergies declines among adults to only 12% of all food allergies [2][3][4].
Clinical symptoms can vary by severity and organs affected.Symptomatology includes gastro-intestinal complaints, dyspnoea, cutaneous reactions, and anaphylactic shock.The severity of an allergic reaction depends upon sensitization, allergen amount, and type of exposure [4].The variability of clincial signs and symptoms is a challenge for the allergologist to advise patients in risk management.
In recent years, molecular diagnostics in allergology have become reality.By detailed knowledge of relevant allergens in complex allergen sources such as food, a tailored risk management is facilitated.
With the following case reports we want to illustrate modern risk management in food allergies.

Case Report
Case 1: A 54-year-old female patient experienced lip swelling, nausea and thoracic pressure immediately after lunch.The meal consisted of quail eggs -sunny side up-, mashed potatoes, red cabbage, pasta with tomato sauce, and beer.Medical emergency treatment was successful.
In consequence of this event she avoided quail eggs, the only new food component.Hen's eggs were consumed by the patient only hard boiled, what was well tolerated.
After detailed medical history, we performed prick tests with the foods.The prick test for native hen's egg was positive (Fig. 1).Laboratory investigations demonstrated specific IgE against ovalbumin 0.88 kUA/l (CAP-class 2), but not against any other egg component.
Case 2: A 40-year-old female patient reported about pharyngeal tingling sensations and abdominal pain after consumption of boiled eggs for years.After detailed medical history a prick test was performed, that revealed a positive reaction to native hen's egg.Laboratory investigated disclosed specific IgE against ovalbumin (0.77 kUA/l, CAP-class 2) and ovomucoid (0.49 kUA/l, CAP-class 1).
Limitations: Double-blinded oral provocation is used for confirmation of food allergies.However, in practise, not all patients will agree to perform the oral challenge.Both of our patients refused oral provocation, since they remained without further allergic reactions to egg proteins after diagnostics and counselling.

Discussion
Egg allergies can usually be confirmed by the combination of medical history, prick test, and specific IgE.Prick test with native hen's egg is more sensitive that with commercial egg extracts [4,5].It must be kept in mind that different assays for specific IgE provide variable, not uniformous results considering the absolute values.In case of follow-up to verify immune tolerance development, the same assay should be used [6].

Risk Management in Case of Egg Allergy
Copyright: © 2016 Wollina et al.
Egg allergens are often hidden allergens in food.An investigation of snacks and pastries identified undeclared egg allergens in 12% and 6% of cases [7].That is a source of discomfiture among consumers.Egg allergies rank on foremost position for smaller children in the Germany Anaphylaxis Registry [8].
Molecular allergy represents a milestone the diagnostic of food allergies.For the first time, tailored risk profiles can be assessed for individual patients.Patients can be counselled accordingly to avoid the identified allergens or to prepare the food -in case of thermolabile allergens -in a proper way.This will reduce the risk of severe allergic reactions [9].A limitation is, however, that most clinical trials have been performed in small children, not adults.Ovalbumin represents 54% of egg proteins [1][2][3][4]9].Ovalbumin ist thermo-labile.A fried egg -sunny side up -had enough native ovalbumin to induce an allergic reaction in patient #1.Hard boild eggs or deeply fried eggs don't imposes a risk for the patients [2,4], illustrated nicely by the symptless consumption of hard boild hen's eggs in case 1.
In contrast, ovomucoid is thermo-stabile and resistant to digestion.Ovalbumin is the dominant allergen component of hen's eggs and represents 11% of hen's eggs protein amount [3,4].The protein can be identified in small amounts not only in food but vaccines against yellow fever and influenca.This might theoretically cause problems in highly sensitized patients.A Japanese study investigated the risk of influenca vaccination in children allergic to eggs but could not find any allergic reactions to the vaccine [10].
Low-level specific IgE against ovomucoid may be a hint for mild symptoms after consumption of boiled eggs as in case 2 or of tolerance induction.A failure of tolerance development is often associated with increased specific IgE againts ovomucoid [5].
There is a case report of a child without hen's egg allergy who developed food-protein enterocolitis syndrome after consumption of quail eggs.Such reaction is not IgE mediated.Due to diarrhoea and vomiting allergic shock can be seen in up to 20 % of patients [11].
Patients with ovomucoid-allergy are not protected by food processing.Strict avoidance of eggs or oral tolerance induction are the alternatives.Recently, monoclonal IgE antibody omalizumab has been used off-label in such cases [12].

Table 1 :
Pros and Cons of Molecular Diagnostics