Allergens in eggs

Any food, ingredient or additive may contain substances capable of causing allergic reactions. Eggs are one of the foods that most frequently cause adverse reactions that have to be treated in health centers. Foods containing egg or milk are the ones that most affect children under two years of age.

Characteristics of allergic reactions to eggs:

• Symptoms due to egg allergies usually appear before the age of two, and usually disappear before the age of six.
• Children may be sensitized to eggs prior to their introduction into the diet for two main reasons, namely:

Inadvertent contacts through contamination of the child's food with egg particles occur when egg-containing particles are passed into the child's food through hands, cooking utensils, etc., due to inadequate hygienic practices.

Exposure to egg proteins through breast milk. The most frequent symptoms can be skin reactions, followed by gastrointestinal and respiratory symptoms, and can even become more severe, turning into anaphylactic reactions.

Proteins in the egg white and yolk can act as aeroallergens and cause asthma. Some people may suffer from urticaria due to contact with eggs and yet tolerate their ingestion.

Reactions to raw eggs are more frequent than to cooked eggs. Allergic reactions to eggs usually appear within the first hour after ingestion. Egg reactivity is a risk marker for sensitization to aeroallergens, and development of rhinitis and asthma from 5 years of age, with a higher incidence if atopic dermatitis is present.

There is cross-reactivity between egg white and yolk proteins, and between eggs from different birds (chicken, turkey, duck). The risk of cross-reactivity between egg and chicken meat is low, approximately only 5%. Allergenic components in eggs: Egg-allergic children usually react to ingestion of the egg white, although the yolk has several proteins, the white contains the major allergens.Allergens present in egg whites:

• Ovomucoid: 11%: this is the most important protein as a cause of allergic reaction, due to its greater resistance to heat and digestive enzymatic action. It is allergenic in minimal quantities.

• Ovalbumin: 54%.

• Ovotransferrin or conalbumin: 12%.

• Ovomucin: 1.5%.

• Lysozyme: 3.5%.

Allergens present in egg yolk:

• Granules.

• Livetins: present in yolk, meat and chicken feathers, which explains why the patient presents allergy symptoms when inhaling feather particles or eating chicken egg or meat.

• Low-density lipoproteins.

Food additives (e-numbers), which may contain egg:

• Lecithin (e-322): used as an emulsifier. When its origin is not specified (usually soybean).

• Lysozyme (e-1105): used to cure cheese.

• Lutein (e-e-161b): mostly used as a yellow pigment.

• Albumin: used as a stabilizer and thickener, present in many candies, margarines and salad creams.

• Ovalbumin.

• Conalbumin.

• Ovomucoid.

• Ovomucin.

• Ovomacroglobulin

• Apritelenins.

• Phosvitin/liveins/alpha-livenin.

Egg allergens can be found in vaccines incubated in eggs.

Example: influenza vaccine and yellow fever vaccine. Some medications, vitamin preparations or nasal drops contain lysozyme and other egg derivatives are found in some anesthetic inducers. Treatment and recommendations for those allergic to eggs:

• Do not ingest eggs or egg-containing products.

Avoid the presence of egg particles in foods that do not originally contain them. This is achieved by taking extreme hygienic measures to eliminate possible egg residues that may remain on surfaces, kitchen utensils, hands, etc.

Be attentive to the labels of industrial foods to detect the presence of egg in the ingredients, or in the list of additives. When not eating at home, ask about the ingredients and mode of preparation of foods to avoid ingestion of those that may contain eggs.

It is recommended to monitor the evolution of skin and laboratory tests against egg proteins every one or two years, to know the degree of sensitization and to schedule provocation tests, in order to demonstrate tolerance and introduce egg in the diet.