Allergen Profile, Egg White, IgE With Component Reflexes*

Allergen-specific IgE assays do not demonstrate absolute positive and negative predictive values for allergic disease. Clinical history must be incorporated into the diagnostic determination. Although the use of component resolved IgE testing may enhance the evaluation of potentially allergic individuals over the use of whole extracts alone, it cannot yet replace clinical history and oral food challenge in most cases. Sensitization against thus far unidentified determinants that are not found in the whole extract or in components might cause symptoms in rare cases.

Egg Allergy

 

After cow’s milk, allergy to hen’s egg is the second most common allergy in infants and young children, affecting 1% to 2% of this population.^5-9 A significant portion of children with hen’s egg allergy will outgrow their allergy.^5,6 Egg allergy can cause severe allergic reactions in sensitized children and egg avoidance can cause significant dietary limitations. Several studies suggest that early sensitization to egg is a precursor to later sensitization to aeroallergens and the development of asthma.^5,6

Egg Components

Ovomucoid (Gal d 1)

 

After cow’s milk, allergy to hen’s egg is the second most common allergy in infants and young children, affecting 1% to 2% of this population.^5-9 A significant portion of children with hen’s egg allergy will outgrow their allergy.^5,6 Egg allergy can cause severe allergic reactions in sensitized children and egg avoidance can cause significant dietary limitations. Several studies suggest that early sensitization to egg is a precursor to later sensitization to aeroallergens and the development of asthma.^5,6

Egg Components

Ovomucoid (Gal d 1)

• Gal d 1 is the dominant egg allergen; it is highly allergenic and very stable to heat.^8-11

• High levels of specific IgE antibodies to Gal d 1 indicate persistent egg allergy.^8,12,13

• Low levels of specific IgE antibodies to Gal d 1 in early infancy suggest a good prognosis for outgrowing the egg allergy.¹⁴

• Gal d 1 specific IgE levels over time generally decrease as tolerance develops.¹⁴

• The majority of children with egg allergy will tolerate extensively heated or baked egg.^7,15

• Significant levels of specific IgE antibodies to Gal d 1 indicate a risk for clinical reactions to both raw and cooked egg.^15,16

• Children with low or undetectable levels of IgE antibodies to Gal d 1 have a high likelihood of tolerating boiled egg and extensively heated egg, eg, in cakes and cookies.^7,12,15,16

• Quantification of Gal d 1-specific IgE can be useful in guiding the physician in the decision when to perform an oral food challenge test as well as to reduce the risk of serious reactions during OFC.^9,16-19

^{Ovalbumin (Gal d 2)}

• Gal d 2 is the most abundant protein in egg, but is easily denatured when heated.^9,10,20

• Egg allergic patients sensitized to Gal d 2 may experience allergic reactions upon influenza and yellow fever vaccinations.²¹