Understanding an Egg Allergy

In Singapore, egg allergy is one of the most common food allergies seen in young infants and children, together with cow’s milk allergy. A person develops an allergic reaction to eggs when the body inadvertently recognises egg proteins as a foreign or dangerous substance and mounts an exaggerated immunological response. 

The clinical manifestation of egg allergy can range from mild symptoms such as hives, rhinitis, and eczema to severe life-threatening allergic reactions such as anaphylaxis. Thankfully, most people with an egg allergy experience mild symptoms, and most children who experience an egg allergy tend to outgrow the symptoms over time.

What are the symptoms of an egg allergy?

The allergic response to eggs may vary from one person to another. Symptoms may occur within minutes or hours following consuming eggs or food which contains eggs. 

Most allergic symptoms are mild, though occasionally, one can develop life-threatening symptoms following the consumption of eggs. Allergy symptoms can affect multiple organs of the body:

Dermatological symptoms

• Hives/wheals
• Eczema
• Itching

Respiratory symptoms

• Snuffly nose, sinus congestion
• Watery, itchy eyes
• Itchy throat
• Cough
• Wheezing
• Shortness of breath

Gastrointestinal symptoms

• Bloatedness
• Nausea and vomiting
• Diarrhoea

Rarely, one may develop anaphylaxis. This is a very serious medical condition that warrants immediate medical attention as one can succumb to the allergy.

Symptoms are systemic; always remember the algorithm A-B-C:

• Airway: tightening of the throat/tongue or lip swelling, difficulty swallowing, hoarseness of voice.
• Breathing: difficulty breathing, noisy or wheezy breathing.
• Circulation: dizzy, cold clammy skin, confused, drowsy, loss of consciousness, collapse.

If you or your loved ones develop any symptoms of A-B-C, please seek medical assistance immediately. Don’t delay; anaphylaxis is reversible if managed promptly.

What are the risk factors for developing an egg allergy?

• Strong family history: egg allergy is more common if one has a strong family history of food allergy and atopy.
• History of atopy: egg allergy is more prevalent in those with atopic conditions such as asthma, eczema, and allergic rhinitis.
• Young age: egg allergy is more frequent in infants and tends to outgrow over time.

Which part of the egg causes the allergy? The white or the yolk?

The proteins found in an egg's white and yolk can cause an allergic reaction, though it is far more common for one to be allergic to the white of the egg.

Allergen proteins in the egg white, such as ovomucoid, ovalbumin, ovotransferrin, and lysozyme, are allergens commonly associated with egg allergies.

The egg yolk contains a protein known as alpha-livetin. This protein plays a role in an allergy condition known as bird-egg syndrome. This is a condition where a person is firstly exposed and sensitised to airborne related bird allergens, with a subsequent secondary exposure and sensitisation to egg yolk protein. Patients with this medical condition present with respiratory symptoms such as asthma or rhinitis following exposure to the bird and eating the eggs.

So why do we develop an allergic reaction from the egg proteins? Simply put, the ability to cause allergy to the protein can be correlated to their resistance against the gut's digestive enzymes and heat. The more robust the egg proteins are against heat and digestive enzymes, the more likely they can elicit an immune response. This is seen in people who are allergic to ovamucoid protein, which is more ‘heat-stable’ and ‘stable against digestive enzymes’, where they may have more persistent allergy symptoms than people who are allergic to other types of egg proteins.

When should I see my doctor regarding egg allergy?

If you develop the allergy symptoms discussed above and are concerned about egg allergy, you can visit your doctor to test for the possible allergy. Your doctor may work with you to review the potential allergies based on your symptoms and advise accordingly.

How can I diagnose an egg allergy?

Diagnosis of egg allergy is based on a strong history and physical symptoms of allergy and the positive correlation with egg consumption.  Depending on the individual case, your doctor may advise you for allergy tests in the form of skin prick or blood (RAST) tests to evaluate the possible allergy further. 

There are available allergy tests for the whole egg, the egg white, the egg yolk, or even the individual egg proteins. You may be advised to temporarily eliminate eggs from your diet and reintroduce them back to your diet later under medical guidance.

How can I treat an egg allergy?

The only treatment for food allergies is avoiding the food particles that cause the allergy- in the case of egg allergy –  to avoid eggs.

For mild symptoms, your doctor may prescribe antihistamines and other symptomatic relievers to manage your allergy symptoms. In those who are at risk of anaphylaxis, your doctor may prescribe you an adrenaline injection pen to use in dire circumstances. 

In the case of food allergy, it is important to read food labels before consuming food. While eating out, it is always important to remind the kitchen/chef of your food allergy. If you are breastfeeding and your child has an egg allergy, do avoid food that contains eggs, as the allergic protein can be passed on through breast milk to your child.

Is a well-cooked/ processed egg suitable for a person with an egg allergy?

Medical literature reveals that patients with an egg allergy may be able to tolerate highly heated or baked/processed eggs (muffins/cookies). This is due to the possible denaturing of the allergenic protein by high heat, allowing patients to tolerate food with eggs. However, it is difficult to identify such a group of patients unless the patients are determined through an oral food challenge test. 

This should be practised cautiously as severe allergy can occur during oral food challenge tests. You are advised to discuss with your doctor before trying processed or high-heated eggs if you have a history of egg allergy.

Vaccination Safety and Egg Allergy

• Influenza vaccine: the World Health Organization (WHO) recommends flu vaccines to people appropriate for their age and health status regardless of whether they are allergic to eggs. Children with severe life-threatening egg allergic symptoms can take their flu vaccine but are advised to get vaccinated in medical settings equipped with immediate allergic treatment.
• MMR vaccine: there is a common public misconception that MMR is contraindicated in patients with egg allergy. Although the MMR vaccine is developed in the embryo cells of the chicken, it does not contain any egg proteins; hence, it is safe for children with egg allergies.

• Yellow fever vaccine: there are reported allergic reactions to the vaccine in egg allergy patients. For those required to consider vaccination before travelling to endemic countries, you are advised to speak to your allergist about the risks and benefits of vaccination vs. the severity of an allergic reaction. Your allergist will guide you further on whether to proceed with vaccination.

What have I learnt today…

• Egg allergy is common in children.
• There are diverse symptoms of egg allergies- ranging from mild symptoms to possible anaphylaxis.
• One can be allergic to the white and the yolk of eggs.
• Treatment is via avoidance. In severe cases, carrying a standby adrenaline injection pen is advisable to reverse the allergy.
• There are allergy tests available to evaluate egg allergy. Speak to your trusted healthcare provider to further understand egg allergy and testing!

References:

1. Caubet JC, Wang J. Current understanding of egg allergy. Pediatr Clin North Am. 2011 Apr;58(2):427-43.
2. Konstantinou GN, Giavi S, Kalobatsou A, et al. Consumption of heat-treated egg by children allergic or sensitised to egg can affect the natural course of egg allergy: hypothesis-generating observations. J Allergy Clin Immunol. 2008;122(2):414–5.
3. Lemon-Mule H, Sampson HA, Sicherer SH, et al. Immunologic changes in children with egg allergy ingesting extensively heated eggs. J Allergy Clin Immunol. 2008;122(5):977,983, e1. 
4. https://www.cdc.gov/flu/prevent/egg-allergies.htm
5. https://www.healthhub.sg/live-healthy/influenza_vaccine_for_your_child#:~:text=The%20influenza%20vaccine%20is%20also,tenderness%20at%20the%20injection%20site.
6. National Advisory Committee on Immunization (NACI). Egg allergy and MMR vaccine: New recommendations from the National Advisory Committee on Immunization. Can J Infect Dis. 1996 Sep;7(5):289-90.
7. https://www.cdc.gov/yellowfever/qa/index.html#novaccine