Egg is one of the most important allergens in childhood feeding, and egg allergy can pose quality-of-life concerns. A clear clinical history and the detection of egg white–specific immunoglobulin E (IgE) will confirm the diagnosis of IgE-mediated reactions. Non–IgE-mediated symptoms, such as those of eosinophilic diseases of the gut, might also be observed. Egg avoidance and education regarding the treatment of allergic reactions are the cornerstones of management of egg allergy. This article discusses epidemiology, risk factors, diagnosis, treatment, and natural history of egg allergy.
After cow’s milk, hen’s egg allergy is the second most common food allergy in infants and young children. The estimated prevalence of egg allergy varies depending on method of data collection or definition. A recent meta-analysis of the prevalence of food allergy estimated that egg allergy affects 0.5% to 2.5% of young children. The major limitation of this meta-analysis was significant variability in study design that made direct comparisons difficult. Most studies included in the meta-analysis were based on self-reports of food allergy, which tend to overestimate the prevalence. Some studies used skin prick test and food-specific IgE levels to confirm sensitization to the allergen; however, only 3 studies used double-blind, placebo-controlled food challenges, the gold standard, to confirm the diagnosis of food allergy. In these 3 studies of unselected populations, the prevalence of egg allergy ranged from 0.0004% in a cohort of German children aged up to 17 years, to 0.6% in nursery school children in Mexico, to 1.6% in 3-year-old Danish children. From Norway, Eggesbo and colleagues reported an estimated point prevalence of allergy to egg in children aged 2.5 years of 1.6% (confidence interval [CI] 1.3%–2.0%), with an upper estimate of the cumulative incidence by this age calculated roughly at 2.6% (CI 1.6%–3.6). A similar prevalence of 1.3% was reported from the United States. Although prevalence depends primarily on nutritional habits in different population, the heterogeneity in egg allergy prevalence may not reflect genuine difference between populations but may be related only to difference in the design and conduct of the primary studies. Egg allergy is closely associated with atopic dermatitis and was found to be present in about two-thirds of children with positive oral food challenges (OFC) performed for allergy evaluation of atopic dermatitis. The risks of sensitization to aeroallergens and asthma are also increased in children with egg allergy.
Pathogenesis
Egg allergy may be defined as an adverse reaction of immunologic nature induced by egg proteins, and includes IgE antibody–mediated allergy as well as other allergic syndromes such as atopic dermatitis and eosinophilic esophagitis, which are mixed IgE-mediated and cell-mediated disorders. IgE-mediated food allergy, also known as type I food allergy, accounts for most of the food-induced responses and is characterized by the presence of allergen-specific IgE antibodies. Five major allergenic proteins from the egg of the domestic chicken ( Gallus domesticus ) have been identified; these are designated Gal d 1 to Gal d 5. Most of the allergenic egg proteins are found in egg white ( Table 1 ), including ovomucoid (Gal d 1, 11%), ovalbumin (Gal d 2, 54%), ovotransferrin (Gal d 3, 12%), and lysozyme (Gal d 4, 3.4%). Although ovalbumin (OVA) is the most abundant protein in hen’s egg white, ovomucoid (OVM) has been shown to be the dominant allergen in egg.
| IgE Binding Activity | ||||||||
|---|---|---|---|---|---|---|---|---|
| Allergen | Common Name | Content (%) | Mw (kDa) | Carbohydrate (%) | Digestive | Allergenic Activity | Test Code (In Vitro Tests) | |
| Heat Treated | Enzyme Treated | |||||||
| Gal d 1 | Ovomucoid | 11 | 28 | 25 | Stable | Stable | +++ | f233 |
| Gal d 2 | Ovalbumin | 54 | 45 | 3 | Unstable | Unstable | ++ | f232 |
| Gal d 3 | Ovotransferrin/conalbumin | 12 | 76.6 | 2.6 | Unstable | Unstable | + | f323 |
| Gal d 4 | Lysozyme | 3.4 | 14.3 | 0 | Unstable | Unstable | ++ | k208 |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
