November 10, 2008

Children with Egg Allergies May Tolerate Heated Egg

Photo of hand breaking egg into bowl

A new study has found that the majority of children with egg allergy may be able to eat some baked foods containing egg. The early results also raise the possibility that the gradual introduction of extensively heated egg may help alleviate some children's allergy to regular egg.

Egg allergy is among the leading food allergies in children, affecting approximately 1.6% of children in the United States. Children with egg allergy can't eat any foods that contain egg, including salad dressings and cake frostings. It was once believed that all children with the allergy outgrew it over time, but the persistence of egg white allergy in older children, into their teenage years, is just beginning to be recognized.

The major protein in hen eggs that triggers the immune system is ovomucoid. Most proteins begin to break down when even briefly heated to temperatures slightly higher than body temperature. Ovomucoid, however, is highly resistant to heating and only breaks up when heated at high temperatures for longer periods. Extended heating, such as baking in the oven, therefore, might reduce its ability to trigger an immune reaction.

In fact, previous reports have suggested that children with egg allergy can eat foods containing heated egg and not have a reaction. A research team led by Dr. Anna Nowak-Wegrzyn at New York's Mount Sinai Medical Center sought to explore the relationship between heated egg and the development of immune tolerance to egg. Their work, which was supported by NIH's National Institute of Allergy and Infectious Diseases (NIAID), appeared in the November 2008 issue of The Journal of Allergy and Clinical Immunology.

The study included 117 children with an average age of 7 who were allergic to eggs. Children with recent severe allergic reactions to egg in baked products were excluded for safety reasons. The researchers first measured tolerance to heated egg by feeding the children muffins or waffles containing heated egg. Approximately 70% of the children with egg allergy were tolerant to heated egg during this initial food challenge.

The children who proved tolerant to heated eggs were told to add baked egg products to their diets at home and return for follow-up evaluations every 3-6 months. Over 12 months, the children ingesting baked eggs had decreased allergy test responses to egg white proteins. This result suggests that the children eating heated eggs may be developing tolerance to regular eggs. Further studies will be needed for confirmation.

These results, while preliminary, challenge the current standard of care for children with egg allergy, which is a strict avoidance of products containing egg. With careful monitoring, children with food allergies may be able to safely eat egg products. However, the researchers strongly caution against introducing heated egg into a child's diet without medical supervision. Some children can still have serious allergic reactions to heated eggs.

— by Julie A. Wu, Ph.D.

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