Egg allergy (chicken eggs)

Eggs (chicken eggs) are one of the main causes of allergic reactions in children. However, many of them develop a tolerance to chicken eggs over time and so can tolerate them as they get older. As eggs are a concealed ingredient in many foods, it is important to read the label carefully before buying or consuming them.

Triggers

There are two parts to every egg: the egg white and the egg yolk, which cannot be completely separated from each other. The two most important allergens are ovomucoid and ovalbumin, both of which are found in the egg white.

Ovomucoid is acid resistant and heat stable. People who have an allergic reaction to ovomucoid usually cannot tolerate raw or cooked eggs. Ovalbumin, on the other hand, breaks down at high temperatures and therefore people who have an allergic reaction to ovalbumin can often tolerate cooked eggs.

Presence

Chicken eggs are found in egg dishes and are used as a binding agent in many processed foods. Purchasing guide in German «Einkaufshilfe Ei-Allergie». Caution is also advised with vaccines produced using chicken eggs. Purchasing guide in German by «Einkaufshilfe Ei-Allergie (Hühnerei)»

Cross reactions

Cross reactions can occur:

• between the different chicken egg allergens
• between chicken egg allergens and chicken allergens
• between chicken egg allergens and the allergens in the eggs of other birds
• between chicken egg and chicken meat allergens

Course of the allergy

Chicken egg allergy typically first occurs in infancy and is often outgrown by school age. An annual check with an allergy specialist is recommended. Chicken eggs, together with cow’s milk, are the most common cause of food allergy in childhood.

In adulthood, sufferers typically first develop a respiratory allergy as a result of keeping exotic birds – the triggers are bird droppings and feathers. They may then later develop a food allergy to chicken eggs (egg yolk). This is known as bird-egg syndrome.

Symptoms

As with all other food allergies, egg allergy symptoms appear within minutes to an hour after consumption and typically include itching in the mucous membranes of the mouth and on the skin with redness, wheals and swelling. Like other food allergies, respiratory symptoms may also occur. Isolated gastrointestinal symptoms are rare. They usually occur in combination with other allergy symptoms, such as difficulty swallowing, nausea, vomiting, diarrhoea and bloating. In rare cases, the allergy may result in anaphylactic shock with breathing difficulties and circulatory collapse.

Diagnosis

Self-monitoring – ideally recorded in a symptom diary – and a consultation with an allergy specialist, together with the results of skin and blood tests, are the essential basis for the diagnosis of egg allergy. To confirm the diagnosis and to determine the tolerance level, provocation (or challenge) tests may also be required.

Treatment

Strict avoidance of the food causing the allergy is essential. It is also essential to watch for concealed sources in bakery products, sausage, spice blends and semi-cooked and ready meals. If there is a risk of an anaphylactic reaction, it is essential to strictly avoid even the tiniest amounts (traces / contaminants). Whether traces can be tolerated should be decided by an allergy specialist. They may use a provocation or challenge test to determine the level of tolerance to the allergen.

A specialist dietician can provide helpful support in implementing treatment in daily life. For example, to discuss the use of alternatives to egg, to learn how to read ingredient lists, to receive practical advice and to discuss possible changes to one’s personal daily life. The supply of essential nutrients (protein, vitamins and minerals) should be assessed by a specialist dietician and monitored by the treating paediatrician / doctor.

Anyone who has already suffered a severe allergic reaction should always carry an emergency medical ID card and an emergency kit to ensure prompt treatment of any further severe allergic reaction. In any event, once first aid has been administered, they should then seek medical attention from an emergency doctor or hospital.

Oral immunotherapy

Allergen-specific immunotherapy to egg allergy has been investigated in a number of studies. This involves participants regularly taking gradually increasing tiny amounts of egg under medical supervision so that the immune system gradually becomes accustomed to it. Some initial success has been achieved, but with a high number of undesirable effects, such as allergic reactions. The treatment is not yet generally available to sufferers in clinical practice. We strongly advise against attempting such treatment independently at home.

Labelling of food

The presence of egg in food must be declared in Switzerland and the EU. This means that the ingredient and any products produced from it are clearly labelled and highlighted on the packaging – for example, in bold type, italics or in capital letters. Allergy sufferers should look out for the following terms when buying food items: egg, chicken egg, chicken egg components, egg white powder, whole egg powder, egg white, egg yolk, albumin, conalbumin, livetin, lysozyme, meringue, ovalbumin, ovoglobulin, ovomacroglobulin, ovomucin / ovomucoid, ovotransferrin, ovovitellin, Ovozyme®, Simplesse®, vitellin. Unintentional mixtures / combinations must also be mentioned at the end of the list as follows: “may contain …” or “may contain traces of …”. Sales staff in shops selling food (e.g. bakeries, butcher’s etc) and in restaurants, takeaway kiosks etc must also provide information. By law, information supplied verbally by a professional is adequate.

Anyone who has already suffered a severe allergic reaction should always carry an emergency medical ID card and an emergency kit. If a new, severe allergic reaction occurs, an emergency doctor or a hospital should be consulted.

Specific immunotherapy with food allergens is not yet available. There are on-going studies attempting to develop oral tolerance in those with food allergies. There has been some initial success, but no treatment can yet be offered to sufferers in clinical practice.

Tips and tricks

• Write the allergy-causing foods on a “visiting card” and hand to restaurant staff when ordering.
• Before holidays, have these cards translated into the local language and take them with you.
• When invited round to friends and family, either tell the hosts exactly about your allergy or offer to take something allergen-free with you.
• Check lists of ingredients of familiar foods before buying. The recipes can be changed at any time. If you are not sure, the manufacturers or wholesalers will be glad to provide information. Their contact details can be found on the packaging.
• When shopping, look out for products with the Allergy Seal of Quality, these are particularly suitable for people with allergies and intolerances and are recommended by aha! Swiss Allergy Centre.

Facts and figures

• Chicken eggs are the most common trigger of food allergy in children, especially between the ages of two and three.
• Chicken eggs are one of the most common causes of anaphylaxis in children below the age of six.
• Chicken eggs are the trigger in only 4% of cases of food allergy in adults.

Egg allergy: FAQs

What is lysozyme?

Lysozyme is extracted from chicken eggs and used as an antibacterial agent in different ripened cheeses (e.g. Grana Padano) – but not in Switzerland. The Swiss cheese industry has voluntarily undertaken not to use lysozyme in cheese production. Swiss cheeses such as Sbrinz are therefore a good alternative for anyone with an egg allergy.

Should I be vaccinated if I have an egg allergy?

Only a few vaccines, such as those for influenza and yellow fever, still contain chicken egg. However, this is in such tiny trace amounts that their allergenic potential is extremely low. Only those with a severe egg allergy should be assessed by an allergy specialist prior to vaccination for yellow fever or influenza. It is only in rare cases that any others with an egg allergy should not be vaccinated.

Are cooked eggs better tolerated than raw eggs?

Eggs contain both heat sensitive and heat stable allergens. Depending on the allergen trigger, sufferers can tolerate eggs in well or thoroughly cooked or baked form (at least 180oC). This should be tested only under medical supervision

Is it safe for me to eat vegan products?

Vegan labelled products may contain traces of egg. Whether they can be tolerated or not depends on the individual tolerance level of the egg allergy sufferer.

Must I give up eating eggs and products containing egg for the rest of my life?

Chicken egg allergies typically occur in infancy and early childhood and in most cases are outgrown by school age. An annual check with an allergy specialist is recommended. Adults with an egg allergy, on the hand, usually have to give up eggs for the rest of their lives.

Can the eggs of other birds (e.g. ducks, ostrich, quail...) be eaten by those with a chicken egg allergy?

No. The proteins in chicken eggs resemble those in the eggs of ducks, geese, quail and other birds and hens. Those who have an allergic reaction to chicken eggs are therefore also unable to tolerate the eggs of other birds. This can be tested with the help of an allergy specialist.

Is it possible to become desensitised to chicken eggs?

Much research is currently being conducted on oral desensitisation to chicken eggs. The aim of the treatment is to gradually accustom the immune system to egg white, so that eggs can be consumed without any allergy symptoms. The treatment is not yet generally available to sufferers in clinical practice. Under no circumstances should such a treatment be attempted independently at home.

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.