Egg allergy, like other food allergies, occurs when there is a breakdown in immune system tolerance. Normally, the immune system is unresponsive to egg, but in egg allergy, the immune system becomes sensitized to egg protein and generates egg-specific IgE-antibodies. Upon re-exposure to egg, an IgE-mediated immune response occurs, which causes the release of histamine and other chemical mediators that create the symptoms of an allergic reaction. It’s not known why this loss of tolerance occurs in some people, but it likely involves a combination of genetic predisposition to immune sensitivity to eggs and environmental exposures that bring out such predispositions.[1] Currently, there are two leading theories identified by the National Academy of Sciences, Engineering, and Medicine: The “microbial exposure hypothesis” suggests that reduced exposure to microbes early in life may hinder the development of the early immune system, leading to inappropriate reactivity; the “dual allergen exposure hypothesis” suggests that a damaged skin barrier (e.g., as seen in eczema) may allow for the absorption of food allergens through the skin before they have been introduced orally, leading to sensitization.[1] Ultimately, more research is needed to fully understand what causes egg allergy, and the causes are likely multifactorial.