Egg Allergy: Brief Review

Eight top allergens account for 90 percent of all food allergies. The 8 top allergens can be remembered by the mnemonic TEMPS WFS:

Tree nuts (almonds, cashews, walnuts)
Egg white (not egg yolk)
Milk
Peanuts
Shellfish (crab, lobster, shrimp)
Wheat
Fish (bass, cod, flounder)
Soy


Eight top allergens account for 90 percent of all food allergies. See more Allergy and Immunology mind maps here.

Egg allergy is one of the most common food allergies in young children.

The diagnostic algorithm for food allergy is remembered by the mnemonic SAD F:

1. Symptoms: close relation between specific food intake and symptoms, often affect 2 or more organs.
2. Allergy testing: skin testing, ImmunoCAP.
3. Diagnostic diet: restricted diet leads to symptoms disappearance or significant reduction
4. Food challenge: original symptoms reappear during challenge.

What is the prognosis of egg allergy?

Majority of children outgrow the allergy by school age.

90% of infants allergic to milk and 50 % those allergic to eggs outgrow their clinical reactivity by the age of 3 but most patients allergic to peanuts do not. Therefore, diagnosis should therefore be re-evaluated yearly. There is some evidence that milk and egg allergies are becoming harder to outgrow.

There is a correlation between IgE titres and the severity of clinical reaction to egg after the diagnosis has been established. A cut-off level of 8.20 kU/l had a 90% probability of clinical reactivity. IgE titres may help determine which patients are at risk of a reaction to eggs.

Who will "outgrow" food allergy? It depends on the epitope

Each food is composed of many proteins and these proteins have multiple areas, termed epitopes, to which the immune system can respond. Epitopes that are dependent upon the folding of the proteins are called conformational epitopes. Epitopes that are not dependent upon folding are called linear epitopes.

A linear epitope oftens means a more prolonged allergy which is “stable” and persistent. A conformational epitope (egg, milk) often means a mild, transient allergy.

What is the treatment of egg allergy?

Management of egg allergy involves exclusion of egg from the diet.

There is no current active treatment for food allergy. Traditional injection immunotherapy (SCIT) has been proved unsafe, and therefore there is a need for other forms of immunotherapy. Occasional studies of egg oral immunotherapy (OIT) are currently at the stage of proof of concept.

Potentially life-threatening reactions may arise from immunization with vaccines prepared in eggs.

EpiPen Jr. is life saving in cases of anaphylaxis.

When is diet elimination no longer required in egg allergy?

This decision may be helped by:

- demonstrating loss of sensitivity by skin prick or specific IgE testing
- supervised food challenge

Is it true that egg allergy is no longer considered a contraindication to MMR vaccine?

Several studies have documented the safety of measles and mumps vaccine (which are grown in chick embryo tissue culture) in children with severe egg allergy. Neither the AAP's "Red Book" Committee nor ACIP consider egg allergy as a contraindication to MMR vaccine. ACIP recommends routine vaccination of egg-allergic children without the use of special protocols or desensitization procedures. The MMR vaccine is grown on fibroblasts and is generally free of egg protein. MMR can be administered safely to all egg-allergic children.

Source: National Center for Immunization and Respiratory Diseases (Grant No. 5U38IP000290) at the Centers for Disease Control and Prevention (CDC), http://www.immunize.org/askexperts/experts_mmr.asp

Influenza vaccine

In 2008, the Advisory Committee on Immunization Practices recommended that all children get flu shots except infants younger than 6 months and those with serious egg allergies.

Egg-allergic patients without anaphylaxis to egg may safely receive the influenza vaccine in a 2-dose, graded fashion without a vaccine skin test. Safety of Influenza Vaccine Administration in Egg-Allergic Patients. Pediatrics, Vol. 125 No. 5 May 2010, pp. e1024-e1030.

References:

Egg allergy. Kemp AS. Pediatr Allergy Immunol 2007: 18: 696–702.
Food Allergy: A Short Review. Allergy Cases.
Clinical review: ABC of allergies, Food allergy. BMJ 1998;316:1299, figure.
RCP: New recommendations for MMR vaccine in egg-allergic children. BSACI Paediatric Allergy Group, Politics.co.uk.
Egg oral immunotherapy in nonanaphylactic children with egg allergy. JACI, Volume 119, Issue 1, Pages 199-205 (January 2007).
Milk and Egg Allergies Harder To Outgrow, Hopkins Study Shows. Johns Hopkins Children's Center, 01/2008.
Correlation between specific immunoglobulin E levels and the severity of reactions in egg allergic patients. Avigael H. Benhamou, Samuel A. Zamora, Philippe A. Eigenmann. Pediatric Allergy and Immunology 19 (2), 173–179, 2008.
Tolerance to egg-containing baked foods (cake, bread) does not exclude the possibility of egg allergy (AAAAI Ask The Expert).
Image source: Wikipedia, public domain.

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