Egg allergy is an immune hypersensitivity to proteins found in chicken eggs, and possibly goose, duck, or turkey eggs. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus.National Report of the Expert Panel on Food Allergy Research, NIH-NIAID 2003
In the United States, 90% of allergic responses to foods are caused by cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, soybeans, and sesame seeds."Food Allergy Facts" Asthma and Allergy Foundation of America The declaration of the presence of trace amounts of allergens in foods is not mandatory in any country, except for Brazil.
Prevention is by avoiding eating eggs and foods that may contain eggs, such as cake or cookies. It is unclear if the early introduction of the eggs to the diet of babies aged 4–6 months decreases the risk of egg allergies.
Egg allergy appears mainly in children but can persist into adulthood. In the United States, it is the second most common food allergy in children after cow's milk. Most children outgrow egg allergy by the age of five, but some people remain allergic for a lifetime."Egg Allergy Facts" Asthma and Allergy Foundation of America In North America and Western Europe, egg allergy occurs in 0.5% to 2.5% of children under the age of five years. The majority grow out of it by school age, but for roughly one-third, the allergy persists into adulthood. Strong predictors for adult-persistence are anaphylaxis, high egg-specific serum immunoglobulin E (IgE), robust response to the skin prick test, and absence of tolerance to egg-containing baked foods.
Signs and symptoms
Food allergies usually have an onset from minutes to one to two hours. Symptoms may include: rash, hives, itching of mouth, lips, tongue, throat, eyes, skin, or other areas, swelling of lips, tongue, eyelids, or the whole face, difficulty swallowing, runny or congested nose, hoarse voice, wheezing, shortness of breath, diarrhea, abdominal pain, lightheadedness, fainting, nausea, or vomiting. Symptoms of allergies vary from person to person and may vary from incident to incident. Serious danger regarding allergies can begin when the respiratory tract or blood circulation is affected. Wheezing, a blocked airway, and cyanosis can indicate the former, whereas a weak pulse, pale skin, and fainting can indicate the latter. When these symptoms occur, the allergic reaction is called anaphylaxis. Anaphylaxis occurs when IgE antibodies are involved, and areas of the body that are not in direct contact with the food become affected and show severe symptoms. Untreated, this can proceed to vasodilation and a low blood pressure situation called anaphylactic shock.
Young children may exhibit dermatitis/eczema on the face, scalp, and other parts of the body; in older children, knees and elbows are more commonly affected. Children with dermatitis are at a greater than expected risk of also exhibiting asthma and allergic rhinitis.
Causes Eating egg The cause is typically the eating of eggs or foods that contain eggs. Briefly, the immune system overreacts to proteins found in eggs. This allergic reaction may be triggered by small amounts of egg, even egg incorporated into cooked foods, such as cake. People with an allergy to chicken eggs may also be reactive to goose, duck, or turkey eggs.
Vaccines Influenza vaccines are created by injecting a live virus into fertilized chicken eggs. The viruses are harvested, killed and purified, but a residual amount of egg white protein remains. For adults ages 18 and older, there is an option to receive recombinant flu vaccines (RIV3 or RIV4), which are grown on mammalian cell cultures instead of in eggs, and so are not a risk for people with severe egg allergy. Recommendations are that people with a history of mild egg allergy should receive any IIV or RIV vaccine. People with a more severe allergic reaction may also receive any IIV or RIV, but in an inpatient or outpatient medical setting, administered by a healthcare provider. People with a known severe allergic reaction to influenza vaccine (which could be egg protein, gelatin, or the neomycin components of the vaccine) should not receive a flu vaccine.
Each year the American Academy of Pediatrics (AAP) publishes recommendations for the prevention and control of influenza in children. In the 2016-2017 guidelines, a change was made that children with a history of egg allergy may receive the IIV3 or IIV4 vaccine without special precautions. It did, however, state that "Standard vaccination practice should include the ability to respond to acute hypersensitivity reactions." Before this, AAP recommended precautions based on egg allergy history: if no history, immunize; if a history of mild reaction, i.e., hives, immunize in a medical setting with healthcare professionals and resuscitative equipment available; if a history of severe reactions, refer to an allergist.
The measles and mumps parts of the "MMR vaccine" (for measles, mumps, and rubella) are cultured on chick embryo cell culture and contain trace amounts of egg protein. The amount of egg protein is lower than in influenza vaccines, and the risk of an allergic reaction is much lower. One guideline stated that all infants and children should get the two MMR vaccinations, mentioning that "Studies on large numbers of egg-allergic children show there is no increased risk of severe allergic reactions to the vaccines." Another guideline recommended that if a child has a known medical history of severe anaphylaxis reaction to eggs, then the vaccination should be done in a hospital center, and the child be kept for observation for 60 minutes before being allowed to leave. The second guideline also stated that if there was a severe reaction to the first vaccination - which could have been to egg protein or the gelatin and neomycin components of the vaccine - the second is contraindicated.
Exercise as a contributing factor There is a condition called food-dependent, exercise-induced anaphylaxis (FDEIAn). Exercise can trigger hives and more severe symptoms of an allergic reaction. For some people with this condition, exercise alone is not sufficient, nor consumption of a food to which they are mildly allergic sufficient, but when the food in question is consumed within a few hours before high-intensity exercise, the result can be anaphylaxis. Eggs are specifically mentioned as a causative food. One theory is that exercise is stimulating the release of mediators such as histamine from IgE-activated mast cells. Two of the reviews postulate that exercise is not essential for the development of symptoms, but rather that it is one of several augmentation factors, citing evidence that the culprit food in combination with alcohol or aspirin will result in a respiratory anaphylactic reaction.
Mechanisms Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response:
IgE-mediated (classic) – the most common type, manifesting acute changes that occur shortly after eating, and may progress to anaphylaxis Non-IgE mediated – characterized by an immune response not involving immunoglobulin E; may occur hours to days after eating, complicating diagnosis IgE and non-IgE-mediated – a hybrid of the above two types
Allergic reactions are hyperactive responses of the immune system to generally innocuous substances, such as proteins in the foods we eat. Why some proteins trigger allergic reactions while others do not is not entirely clear, although in part thought to be due to resistance to digestion. Because of this, intact or largely intact proteins reach the small intestine, which has a large presence of white blood cells involved in immune reactions.Food Reactions. Allergies . Foodreactions.org. Kent, England. 2005. Accessed 27 Apr 2010. The heat of cooking structurally degrades protein molecules, potentially making them less allergenic.
The pathophysiology of allergic responses can be divided into two phases. The first is an acute response that occurs within minutes to an hour or two of exposure to an allergen. This phase can either subside or progress into a "late-phase reaction," which can substantially prolong the symptoms of a response and result in more tissue damage. In the early stages of acute allergic reaction, lymphocytes previously sensitized to a specific protein or protein fraction react by quickly producing a particular type of antibody known as secreted IgE (sIgE), which circulates in the blood and binds to IgE-specific receptors on the surface of other kinds of immune cells called mast cells and basophils. Both of these are involved in the acute inflammatory response. Activated mast cells and basophils undergo a process called degranulation, during which they release histamine and other inflammatory chemical mediators called (cytokines, interleukins, leukotrienes, and prostaglandins) into the surrounding tissue causing several systemic effects, such as vasodilation, mucous secretion, nerve stimulation, and smooth-muscle contraction. This results in runny nose, itchiness, shortness of breath, and potentially anaphylaxis. Depending on the individual, the allergen, and the mode of introduction, the symptoms can be system-wide (classical anaphylaxis) or localized to particular body systems; asthma is localized to the respiratory system while eczema is localized to the skin.
After the chemical mediators of the acute response subside, late-phase responses can often occur due to the migration of other white blood cells such as neutrophils, lymphocytes, eosinophils, and macrophages to the initial reaction sites. This is usually seen 2–24 hours after the original reaction. Cytokines from mast cells may also play a role in the persistence of long-term effects. Late-phase responses seen in asthma are slightly different from those seen in other allergic responses, although they are still caused by the release of mediators from eosinophils.
Five major allergenic proteins from the egg of the domestic chicken (Gallus domesticus) have been identified; these are designated Gal d 1–5. Four of these are in egg white: ovomucoid (Gal d 1), ovalbumin (Gal d 2), ovotransferrin (Gal d 3), and lysozyme (Gal d 4). Of these, ovomucoid is the dominant allergen, and one that is less likely to be outgrown as children get older. Ingestion of under-cooked egg may trigger more severe clinical reactions than well-cooked egg. In egg yolk, alpha-livetin (Gal d 5) is the major allergen, but various vitellins may also trigger a reaction. People allergic to alpha-livetin may experience respiratory symptoms such as rhinitis and/or asthma when exposed to chickens, because the yolk protein is also found in live birds. In addition to IgE-mediated responses, egg allergy can manifest as atopic dermatitis, especially in infants and young children. Some will display both, so that a child could react to an oral food challenge with allergic symptoms, followed a day or two later with a flare-up of atopic dermatitis and/or gastrointestinal symptoms, including allergic eosinophilic esophagitis.
Non-allergic intolerance Egg whites, which are potentially histamine liberators, also provoke a nonallergic response in some people. In this situation, proteins in egg white directly trigger the release of histamine from mast cells. Because this mechanism is classified as a pharmacological reaction, or "pseudoallergy", the condition is considered a food intolerance instead of a true immunoglobulin E (IgE) based allergic reaction.