INTRODUCTION — The management of hen's egg (HE) allergy does not differ from that of other food allergies [1]. It requires instructions on avoidance and education about treatment of reactions in the event of accidental exposure. It also includes monitoring for the resolution of the allergy. (See "Management of food allergy: Avoidance" and "Anaphylaxis: Emergency treatment" and "Food allergy in children: Prevalence, natural history, and monitoring for resolution".)
This topic reviews various aspects of management of HE allergy, including instructions about avoidance of HE protein, education in the proper management of accidental exposures, and monitoring for resolution of the allergy. Issues with HE-containing vaccines and lipid emulsions are also covered in this topic, although options for administration of the influenza vaccine in patients with HE allergy are discussed separately. The epidemiology, pathogenesis, clinical features, and diagnosis of HE allergy are also discussed separately. (See "Egg allergy: Clinical features and diagnosis" and "Influenza vaccination in individuals with egg allergy".)
The management of food allergy in the specific settings of schools and camps is discussed in detail separately. (See "Food allergy in schools and camps" and "Food allergy in college and university students: Overview and management".)
General discussions of food allergy are presented separately in appropriate topic reviews.
AVOIDANCE — The most straightforward approach in managing any food allergy is complete avoidance of the culprit food. Eliminating HE (both egg white and egg yolk) from the diet can be difficult and can pose nutritional as well as quality-of-life concerns since HE is a ubiquitous food in many cultures and diets. HE is an ingredient in baked goods, breaded foods, cream fillings, custards, candies, canned soups, casseroles, frostings, ice creams, lollipops, marshmallows, marzipan, pastas, salad dressings, and meat-based dishes such as meatballs or meatloaf (Food Allergy Research and Education [FARE]). Accidental exposures are common. In one prospective series of 500 infants aged 3 to 15 months with suspected or confirmed HE and/or cow's milk allergy (CMA), 72 percent had an allergic reaction, most commonly to CM, HE, or peanut, during a three-year period, with an annualized reaction rate of 0.81 per year [2]. Twenty-one percent of these were triggered by HE, giving an annualized rate of reaction to HE of 0.17 per year. Eighty-seven percent of all reactions were due to accidental exposures. (See "Management of food allergy: Nutritional issues" and "Food allergy: Impact on health-related quality of life" and "Management of food allergy: Avoidance" and "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Role of avoidance'.)
Counseling about avoidance should include discussions about the following issues:
●Cross-contact and hidden ingredients – Patients must be counseled about the potential for accidental exposure to food allergens via cross-contact (ie, inadvertent exposure to the allergenic food by contamination of "safe" foods with small amounts of the culprit food). This can happen anywhere food is served, including restaurants and bakeries. In addition, egg whites and shells are used as clarifying agents and can be found in soup stocks, consommés, wine, alcohol-based beverages, and coffee drinks. Egg white is also used as a wash to make bread products shiny. (See "Management of food allergy: Avoidance", section on 'Skills for daily living'.)
●Food labels – Patients must read all food labels (FARE). Legislation has been enacted in the United States and many other countries mandating that the ingredient labels on food packages clearly identify the presence of HE when it is an intended ingredient [3]. (See "Management of food allergy: Avoidance", section on 'Food labeling'.)
●Advisory labeling – Some products in the United States and other countries may have advisory labeling, such as "may contain egg." This type of labeling is generally not currently regulated. The risk of allergic reactions to these products is not known, and the frequency and amount of HE contamination in these products has not been studied. (See "Management of food allergy: Avoidance", section on 'Advisory labeling'.)
●Cross-reactivity – Serologic cross-reactivity with other bird eggs (turkey, duck, goose, seagull, and quail) has been reported [4], and there are case reports suggesting clinical cross-reactivity [5]. A minority of patients with allergy to HE are reactive to chicken meat as well. Chicken serum albumin (Gal d 5) is responsible for this cross-reactivity [6]. Given the low rates of clinical reactivity reported, patients with HE allergy are not routinely advised to avoid other bird eggs or chicken meat. (See "Food allergens: Clinical aspects of cross-reactivity".)
●Egg substitutes – Counseling should include a discussion about HE alternatives and substitutes (table 1 and table 2). Commercial products marketed as "egg substitutes" may have HE ingredients. (See "Management of food allergy: Nutritional issues", section on 'Egg allergy'.)
●Unexpected and nonfood sources – Medications and vaccines may have ingredients derived from HE. Patients should ensure that the clinicians and pharmacists caring for them are aware of their HE allergy, especially before receiving any new medication or vaccine. Labeling of nonfood items is not strictly regulated in the United States and most other countries. The yellow fever vaccine may induce reactions in HE-allergic individuals. Protocols are available for the safe administration of this vaccine in HE-allergic individuals. In contrast, the measles, mumps, and rubella (MMR) vaccine and influenza vaccine are well tolerated by persons with HE allergy and should be administered in the routine manner without testing or special precautions. (See "Management of food allergy: Avoidance", section on 'Food allergens in nonfood items' and "Allergic reactions to vaccines", section on 'Egg' and "Immunizations for travel", section on 'Yellow fever vaccine' and "Influenza vaccination in individuals with egg allergy".)
The following scenarios illustrate some of the issues involved in the management of HE allergy and our approach to avoidance. Individual clinicians may decide to adopt different strategies depending upon their level of expertise and the resources available (eg, ability to perform oral food challenges [OFCs]). Our approach to reintroducing various forms of HE is discussed below. (See 'Monitoring for resolution and reintroduction' below.)
●If a patient with an allergy to HE in any or all forms or of any severity wishes to avoid all HE, we do not discourage this approach.
●We allow persons to continue to eat HE in more extensively heated or processed forms than what triggered their reaction(s) if they have eaten HE in these forms regularly and in the recent past (similar to passing an OFC). In most cases, this involves patients who reacted to lightly cooked HE (eg, scrambled egg, French toast) but have a history of tolerating extensively heated HE (eg, muffins, waffles). We generally suggest that these patients avoid more intermediate forms of cooked HE, such as meatballs/meatloaf, breaded foods, casseroles, custard, and mayonnaise. Persons who have not eaten extensively heated (baked) HE should undergo a supervised OFC rather than initial home introduction because of the risk of reactions including anaphylaxis [7]. (See 'Extensively heated (baked) HE' below.)
One caveat to this approach that should be discussed with patients is that it is possible that a patient may have a reaction due to ingestion of a larger amount of HE or more lightly cooked HE than usual (eg, normally tolerates HE in muffins but has a reaction when blueberries are used in the muffins and the batter does not cook completely around the blueberries).
●We advise patients who have reacted to intermediately cooked or extensively heated HE to avoid all forms of HE.
MANAGEMENT OF REACTIONS
Acute IgE-mediated reactions — Patients with immunoglobulin E (IgE) mediated HE allergy are at risk for severe reactions (table 3 and table 4), and the severity of symptoms can vary from reaction to reaction [7,8]. Thus, we prescribe epinephrine autoinjectors for all patients with a history of anaphylactic reactions to HE and typically do so for patients with milder IgE-mediated reactions to HE as well. In addition, the patient should have a written anaphylaxis emergency action plan (Anaphylaxis Emergency Action Plan - English) (Anaphylaxis Emergency Action Plan - Spanish). These measures are discussed in detail separately. (See "Anaphylaxis: Emergency treatment" and "Prescribing epinephrine for anaphylaxis self-treatment".)
As with other forms of food allergy, the severity of symptoms in a given individual with HE allergy may vary considerably between reactions. In addition, the severity of an initial reaction does not predict the severity of subsequent reactions. As examples:
●In a small study investigating whether children with HE allergy of varying severity could tolerate extensively heated forms of HE, 18 percent of children who reacted to extensively heated HE and 23 percent who reacted to lightly cooked HE required treatment with epinephrine [7].
●In another series of 167 children that examined dietary advice and adherence in patients with HE allergy, the initial episode was a local reaction in 29 percent, a mild-to-moderate systemic reaction in 31 percent, and a severe systemic reaction in 18 percent [8]. Twenty percent of the children in this study had a subsequent reaction to HE that was more severe than the initial event.
●Children whose only apparent clinical manifestation of food allergy is atopic dermatitis are at risk of an acute systemic reaction upon reintroduction of that food after an elimination diet [9].
●Children with HE allergy are more likely to develop asthma, and concomitant asthma places patients at higher risk for severe allergic reactions to foods [10].
Delayed gastrointestinal reactions — The management of children with non-IgE-mediated HE allergy, including eosinophilic esophagitis and food-protein induced enterocolitis syndrome, is presented in specific topic reviews. (See "Treatment of eosinophilic esophagitis (EoE)" and "Dietary management of eosinophilic esophagitis" and "Food protein-induced enterocolitis syndrome (FPIES)".)
MONITORING FOR RESOLUTION AND REINTRODUCTION — Children with HE allergy should be monitored for resolution of the allergy since most will outgrow the allergy in childhood. Monitoring for resolution includes assessing history of any accidental exposures and reactions, serial testing for sensitization (in vitro and/or skin prick testing [SPT]), and oral food challenges (OFCs). The general steps taken to determine if an allergy has resolved are covered in detail separately. The approach for HE allergy is outlined here. (See "Egg allergy: Clinical features and diagnosis", section on 'Natural course' and "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Monitoring for resolution' and "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Natural history of specific allergies'.)
Factors that improve the odds of passing a challenge include:
●Lower HE-specific IgE levels [11,12].
●Downward trends over time in HE-specific IgE or SPT reaction [13-15].
●Absence of an interval history of symptoms triggered by accidental exposure. Accidental exposures to foods containing HE are common [2]. Thus, the clinical history is often useful in predicting the likelihood of a successful baked HE introduction.
●Fewer failed OFCs, longer interval since last failed OFC, and failure at a higher dose.
Extensively heated (baked) HE — Several studies have indicated that 66 to 88 percent of persons with HE allergy can tolerate extensively heated or baked forms of HE [7,11,16,17]. Supervised OFCs rather than home introduction are recommended to determine whether a person with HE allergy can safely include extensively heated HE in their diet because of the risk of reactions and the predictive limitations of in vitro and SPT.
The potential benefits of including extensively heated HE in the diet, if tolerated, extend beyond improvements in quality of life. Data suggest that tolerance to extensively heated HE is a good prognostic factor for the development of tolerance to less heated forms of HE and that including extensively heated HE in the diet may accelerate the development of tolerance [18,19]. However, consumption of extensively heated HE may also increase the risk of a reaction due to inconsistencies in the amount of HE in baked products leading to a greater exposure or due to incomplete cooking leading to exposure to lightly cooked HE. (See 'Avoidance' above.)
While there is some variation in the predictive value of SPTs with HE extract and specific IgE levels, the data indicate that there is a >80 percent chance that baked HE will be tolerated if egg white-specific IgE (EW-IgE) is <2 kUA/L, whereas a level >10 kUA/L suggests an increased likelihood of reacting to baked HE [7,11,16]. In one series, the pass rate was approximately 50 percent when the EW-IgE was ≤15 kU/L [12]. SPT is less reliable in predicting baked HE challenge outcomes [11,20]. Prick-prick testing with the challenge food was informative in one study, with 100 percent negative predictive values when mean wheal diameters were <3 mm for three different forms of extensively heated HE (cake, frittata, and boiled HE) [17]. This suggests that these patients could introduce extensively heated HE without first undergoing an OFC. However, prick-prick testing with the food is not standardized, and first exposure to baked HE at home is not advised. The utility of measurement of specific IgE to HE components (ovomucoid, ovalbumin) has also not been extensively studied, and results have not consistently correlated with clinical outcomes [12]. (See "Component testing for animal-derived food allergies", section on 'Egg'.)
In those who reacted during baked-HE challenge, 12 to 44 percent had multisystem involvement requiring treatment with intramuscular epinephrine [7,11,21]. In one series of 174 OFCs to baked HE, baked cow's milk (CM), cooked HE, CM, peanut, or tree nuts in 158 children, new symptoms were more likely to appear ≥60 minutes after stopping an OFC for baked HE or baked CM compared with other foods (29 and 21 percent versus 0 to 10 percent, respectively), with one-third of anaphylactic reactions to baked HE beginning more than an hour after the OFC was discontinued [21]. Hypoxemia and hypotension were only observed in baked-HE and baked-CM challenges. In contrast, mucocutaneous reactions were reported less commonly in baked-HE and baked-CM OFCs compared with OFCs to other foods. In all patients with delayed anaphylaxis to HE (baked or cooked), the OFC was ended due to gastrointestinal symptoms that were not treated. Extending the dosing interval, adding more dosing steps, early treatment of subjective symptoms, and/or prolonging the observation time may be warranted in patients who are at higher risk for reacting to baked-HE OFC (eg, higher IgE levels, recent reactions, history of more severe reactions or anaphylaxis). (See "Milk allergy: Management", section on 'Extensively heated (baked) cow's milk'.)
Findings from one study suggest the cooking temperature, cooking time, and final internal temperature of the food are more important than the presence of a wheat matrix. In this study, 54 children with a history of HE allergy and positive SPT to raw HE were skin tested (prick-prick method) to three different forms of extensively heated HE: baked HE in a wheat matrix in the form of a cake that was baked at 180°C (356°F) for at least 30 minutes, baked HE without a wheat matrix in the form of a single HE frittata fried in olive oil for three minutes and then cooked in a 180°C oven for at least 30 minutes, and HE boiled for 10 minutes [17]. All children were then challenged to the cake, regardless of SPT results. Those who passed the cake OFC were sequential challenged to the frittata and then, if that OFC was passed, to the boiled HE. OFC pass rates were 88 percent for the cake, 74 percent for the frittata, and 56 percent for the boiled HE.
Our approach — For patients with lower HE-specific IgE levels (≤2 kU/L) [22,23] or SPT reactions less than or equal to the histamine control on follow-up testing, especially if the clinical history is reassuring, we will offer food challenge initially to lightly cooked (eg, scrambled) HE rather than extensively heated (baked) HE. The chance of success with these challenges is approximately 50 percent (based upon HE-specific IgE levels). Patients who fail the lightly cooked HE challenge are eligible for a challenge to baked HE. Some families prefer to start with the baked-HE challenge as they feel the addition of baked-HE products into the child's diet is a higher priority.
The approach for determining when to try to introduce baked HE is similar to that for baked CM with regard to testing and OFCs (see "Milk allergy: Management", section on 'Monitoring for resolution and reintroduction'). There are no absolute cutoffs that preclude challenge to baked HE. The only caveat is that successful challenges are less commonly seen with high EW-IgE levels compared with CM. Thus, we usually offer baked-HE challenges with EW-IgE levels of ≤10 kU/L (and/or SPT ≤11 mm wheal) and uncommonly offer them with levels >20 kU/L (and/or SPT wheal >15 mm [7]), although other experts may use different cutoff values. In some cases, families may wish to pursue baked-HE challenge with EW-IgE levels >10 kU/L. However, caution is needed because severe reactions can occur from this type of OFC. Other patients (or their parents/caregivers) may prefer to continue avoidance of all HE until it is felt that they are ready for a lightly cooked HE (eg, scrambled egg) challenge. Some have suggested that HE component testing helps predict challenge outcomes, but this was not supported in several studies [12,24-26]. (See "Milk allergy: Management", section on 'Our approach' and "Component testing for animal-derived food allergies", section on 'Egg'.)
The approach to the patient after a baked-HE challenge is highly individualized. Most often, patients are advised to return for reevaluation and possible advancement to lightly cooked HE (eg, scrambled egg or French toast) using food challenge testing approximately every six months. Some allergy specialists allow select patients to gradually advance their diet at home, from baked HE to less heated HE (eg meatballs/meatloaf, breaded foods dipped in HE and baked) to lightly cooked HE. For patients who fail the challenge with just a mild reaction after ingesting a large dose of baked HE, an option is to have them include a smaller amount of baked HE in their diet and slowly increase the amount over time.
MANAGEMENT OF YOUNGER SIBLINGS — Parents/caregivers often inquire about what measures to take to prevent HE allergy (eg, maternal avoidance during pregnancy and lactation) and when to introduce HE in a younger sibling of a child with HE allergy. In these cases, avoidance of HE is not recommended for nursing mothers, nor is delayed introduction of HE beyond six months of age, unless the infant is showing signs of allergic disease. These issues are discussed in greater detail separately. (See "Pathogenesis of food allergy", section on 'Genetics' and "The impact of breastfeeding on the development of allergic disease" and "Primary prevention of allergic disease: Maternal diet in pregnancy and lactation" and "Introducing highly allergenic foods to infants and children", section on 'Introduction in higher-risk populations'.)
FUTURE TREATMENTS — There are no treatments that can cure or provide long-term remission from food allergy. However, several treatment strategies are under investigation. These approaches are either allergen specific or aimed at modulating the overall allergic response. (See "Investigational therapies for food allergy: Immunotherapy and nonspecific therapies" and "Oral immunotherapy for food allergy".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Seasonal influenza vaccination".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)" and "Patient education: Food allergen avoidance (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Management of hen's egg (HE) allergy includes instructions about avoidance of HE-containing products, education in the proper management of accidental exposures, and monitoring for resolution of the allergy (Anaphylaxis Emergency Action Plan - English) (Anaphylaxis Emergency Action Plan - Spanish) (Food Allergy Research and Education [FARE]) (table 1 and table 2). (See 'Introduction' above.)
●The most straightforward approach in managing any food allergy is complete avoidance of the culprit food. However, eliminating HE (both egg white and egg yolk) from the diet can be difficult and can pose nutritional as well as quality-of-life concerns since HE is a ubiquitous food in many cultures and diets. Counseling should include a discussion about HE alternatives and substitutes (table 1 and table 2). In addition, evaluation of the allergy followed by an oral food challenge (OFC) to extensively heated HE is an option since a majority of those with HE allergy will tolerate HE in extensively heated (baked) products, such as a muffin. (See 'Avoidance' above and "Management of food allergy: Nutritional issues" and 'Extensively heated (baked) HE' above.)
●Patients with immunoglobulin E (IgE) mediated HE allergy are at risk for severe reactions, and the severity of symptoms can vary from reaction to reaction. Thus, we prescribe epinephrine autoinjectors for all patients with a history of anaphylactic reactions to HE and typically do so for patients with milder IgE-mediated reactions to HE as well. (See 'Acute IgE-mediated reactions' above.)
●Children with HE allergy should be monitored for resolution of the allergy since most will outgrow the allergy in childhood. Monitoring for resolution includes assessing history of any accidental exposures and reactions, serial testing for sensitization (in vitro and/or skin prick testing [SPT]), and OFCs. (See 'Monitoring for resolution and reintroduction' above.)
