Introduction

What is allergy?

Allergy is an adverse reaction that occurs when the immune system attacks substances that are often harmless, known as allergens (milk, eggs, nuts, fish, dust, pollens, medicine ).¹ The reaction to these allergens is symptomatic and often characterised by swelling, itching, rash, sneezing, and vomiting. As of 2014, based on data gathered from 89 countries, the World Allergy Organisation (WAO) estimated that over 250 million people experience food allergies globally.² Food allergy constitutes most allergies in recent times, although there is no global data to quantify the prevalence of food allergy.¹

Egg allergy is a serious concern, especially in children. This article will provide a better understanding of egg allergies and guides on how to manage the reaction. Egg allergy tends to develop at infancy before age two and in about 55 % of cases, it resolves at or before age six. About 2% of children and 0.1% of adults are affected.⁴

What is egg allergy?

Egg (Gallus gallus) allergy is the overreaction of the body’s immune system to egg proteins both in egg yolk and egg white.¹ More egg-related allergies are caused by the proteins in the egg white rather than the egg yolk.¹ Egg allergy occurs when the affected immune system mistakenly identifies a protein in an egg as harmful. This results in the immune system overreaction by producing body soldiers (Antibodies) known as IgE (Immunoglobulin E).⁵ This reaction is more prevalent in children characterised by vomiting, abdominal pain, diarrhoea and hives.⁶ Egg allergy is usually known to be a childhood condition, however, it remains persistent in some children in adulthood therefore putting them at higher risk.⁷ In the United States egg allergy affects 0.9% of the children and 1.3% of children under 5 years old.⁸ In the United Kingdom egg allergy occurs in about 2% of children and 0.1% of adults.⁹ While in Australia, egg allergy is more prevalent affecting 8.1 % of children aged 1 year old.¹⁰

The four major egg white proteins majorly responsible for egg allergy are: Ovomucoid, Ovalbumin, Ovotransferrin and lysozyme.¹ Additionally, the egg white has more protein than the egg yolk.¹¹

Egg white allergy

Egg white allergy is more common in children than adults.¹ The ovomucoid protein component of egg white is responsible for most allergic reactions.¹² The production of an immune-specific antibody in reaction to the heat and acid-stable protein (Ovomucoid) leads to a severe reaction in affected persons.¹

Egg yolk allergy

Egg yolk allergy is more common in adults.¹³ The egg yolk consists of two allergies that are less reactive in comparison to egg white.¹ The allergens in egg yolk are water-soluble globular glycoprotein, chicken serum albumin and yolk glycoprotein.¹⁴ It is important to note that there is a limited understanding of yolk allergies, although it is currently being researched.¹⁵

Food sources of eggs that have the potential to cause allergy

• Biscuits
• Plain cakes
• Dried egg pasta
• Gravy granules (if they contain eggs)
• Waffles
• Lemon curd
• Boiled eggs, scrambled egg, fried egg, omelette, poached egg
• Egg fried rice
• Mayonnaise
• Some ice creams 
• Hollandaise
• Salad cream
• Bread and butter pudding, among others.¹⁶ 

Risk factors of egg allergy

Individuals with egg allergy may not be aware of it if there is inadequate exposure to egg allergens.¹⁷ Some of the factors that put individuals at higher risk of allergic reactions caused by eggs include:

1. Age: Egg allergy is more common in children than in adults. This can be related to the fact that their immune system is still in the developmental stage
2. Early exposure to eggs at a young age when the immune system is still developing
3. Children with skin conditions such as eczema are at greater risk 
4. Some infants may be exposed to egg protein through their mother's breast milk¹⁸
5. Inhalation of egg protein from the environment
6. Family History: based on conducted research, a child has a 75% likelihood of developing an allergy if both parents suffer from an allergic reaction. Therefore those who have an inherited possibility are at greater risk of suffering from allergies

Symptoms of egg allergy

Reaction to egg protein can be mild, moderate or severe(as in the case of anaphylaxis). Some of the symptoms of egg allergy include:

• Swelling of tongue/lips or both
• Indigestion, diarrhoea, stomach pain, and vomiting, which occur within 2 hours of the allergen(egg) consumption³
• Dizziness
• Weak pulse
• Skin discoloration(pale/blue)
• Breathing difficulty
• Skin rash (atopic dermatitis) especially in children¹⁸
• Anaphylaxis (more severe allergic reaction), although it is rare,¹⁹ can lead to life-threatening emergencies

Diagnosis

1. Assessment of medical history³
2. Physical examination of the patient
3. Allergy tests done on the body (in vivo) such as:
   • Skin prick test
   • Atopy/skin patch test¹
4. Lab-based allergy tests (in vitro), such as 
   • Diagnostic elimination diet: in this case, the allergen (egg) is removed to monitor symptom improvement
   • Oral food challenge involves the patient consuming a small amount of the suspected allergen (egg) under medical supervision to check for reaction³  
5. Measurement of immunoglobulin E antibodies in the egg protein using blood samples³

Treatment

There is no short-term or long-term cure for egg allergy.²⁰ After confirming an allergy to eggs the current treatment includes:

1. Strict avoidance of food, food products and non-food products containing eggs
2. To stop symptoms (itching, swelling) of allergic reactions doctors administer medications such as antihistamines to block the chemical that causes egg allergy.¹ NOTE: Antihistamine should be used with caution to avoid weakening the immune system
3. In case of a severe allergic reaction (Anaphylaxis) a medicine known as Epinephrine is used to stop the reaction
4. Immunotherapy is considered a very safe and efficient way to treat and relieve allergic symptoms. Immunotherapy occurs in two stages:
   • Desensitisation: the allergic person is given a small amount of what they are reacting to (egg), known as allergen
   • Over time the treatment gets better although it takes at least three months for obvious significant improvement to be noticed²⁰ 

Management 

• Always check and read food labels before consumption
• When eating out, highlight your egg allergy and emphasise the need to avoid cross-contamination during meal preparation
• Go for egg-free cooking options, such as the use of vegan recipes, and consult dieticians for recipes
• Egg-free substitute food such as egg-free mayonnaise is also good.
• When purchasing non-food products containing eggs check labels for OVUM or OVO. However, only avoid these products if you react to them¹⁶
• Inform child caregivers or nurseries about egg allergy

Egg allergy and vaccine

• It is important to consider allergic reactions to eggs when administering vaccines such as influenza or yellow fever because they are produced by growing the vaccine in chicken eggs. Some amounts of the protein can remain in the vaccine although very rare¹⁶
• Children with egg allergy and those who have encountered anaphylaxis are safe to take the Measles, mumps and rubella vaccine (MMR)¹⁶

Summary

Egg allergy is one of the most serious food allergies, especially in infants and children. There is no universal data to quantify the occurrence of egg allergy, but available data indicates that it is more common in Australia and the USA. However, some of the affected children tend to outgrow it before adulthood. Some of the risk factors of egg allergy include hereditary from parents, age, and skin conditions(eczema). It is caused by most of the proteins in the egg white and some in the egg. Symptoms of egg allergy range from mild to moderate to severe, characterised by itching, swelling, and stomach discomfort, among others. While egg allergy can not be permanently cured, it can be managed by completely avoiding egg and egg-containing foods and products and cautiously using antihistamines or immunotherapy.

FAQs

Can children outgrow egg allergy?

Yes, children usually outgrow egg allergy before the age of six only a few carry it on to adulthood.

Can people with egg allergy get vaccines?

 Yes, but consult/inform the Doctors first.

What should I do if someone is experiencing egg anaphylaxis?

• Use an epinephrine auto-injector (Epi-pen) immediately if available
• Call emergency service 911

Is there a cure for egg allergy?

No, it can be prevented and managed but not cured.