An egg allergy occurs when the immune system mistakenly identifies proteins in eggs as harmful, triggering an allergic reaction involving IgE antibodies. These allergies are common, especially among infants and young children.
Understanding Egg Allergies
It is possible to be allergic to just egg yolks, just egg whites, or the entire egg. This specificity stems from the different protein compositions in each part, meaning an individual might react to proteins in the yolk but not the white, or vice versa.
Egg whites contain several allergenic proteins, with ovalbumin (Gal d 2) and ovomucoid (Gal d 1) being the most significant. Ovalbumin can be denatured by heat, so some individuals allergic to it might tolerate well-cooked eggs. Ovomucoid, however, is heat-stable, so those sensitive to ovomucoid often react to both raw and cooked egg forms.
In contrast, egg yolks also contain distinct proteins that can trigger allergic reactions, such as livetins (specifically alpha-livetin, also known as chicken serum albumin, or Gal d 5) and apolipoproteins. Alpha-livetin is a major egg yolk allergen, associated with “bird-egg syndrome” where individuals allergic to bird dander cross-react with egg yolk proteins. While egg white allergy is generally more prevalent, reactions to egg yolk can occur and may be outgrown earlier.
Symptoms and Diagnosis
Symptoms of an egg allergy can manifest within minutes to a few hours, ranging from mild to severe. Common reactions include skin issues like hives or eczema, digestive problems such as abdominal pain or vomiting, and respiratory symptoms like wheezing or nasal congestion.
Although less common for yolk-specific allergies, a severe, potentially life-threatening reaction known as anaphylaxis can occur. Symptoms of anaphylaxis include constriction of airways, swelling of the throat or tongue, a sudden drop in blood pressure, or loss of consciousness. Immediate medical attention and treatment with epinephrine are necessary in cases of anaphylaxis.
Diagnosis of an egg allergy typically begins with a thorough medical history. This is often followed by allergy tests, such as skin prick tests, or blood tests that measure specific IgE antibodies to egg proteins, including those found in the yolk like alpha-livetin. In some instances, an oral food challenge, performed under medical supervision, may be conducted to confirm the allergy.
Living with an Egg Yolk Allergy
Managing an egg yolk allergy primarily involves strictly avoiding egg yolks and foods that contain them. This requires careful attention to food labels, as egg components can be present in many processed foods. The Food Allergen Labeling and Consumer Protection Act (FALCPA) mandates that “egg” be clearly listed on packaged foods in the U.S. if it contains egg. However, egg ingredients can appear under various names, such as albumin, livetin, or words starting with “ovo-” like ovalbumin or ovovitellin.
Individuals should be aware of hidden sources of egg yolk in products like some baked goods, sauces, and certain confectioneries. Cross-contamination is another important consideration, which can occur when egg-containing foods come into contact with egg-free foods during preparation or manufacturing. This risk is particularly high in shared kitchens or facilities that process both egg-containing and egg-free products.
For individuals at risk of severe reactions, carrying an epinephrine auto-injector is an important safety measure. Regular follow-ups with an allergist are recommended, especially for children, as many egg allergies, including those specific to egg yolk, may be outgrown over time. An allergist can guide re-evaluation and discuss the potential for reintroducing egg products under controlled conditions.