Natural course of sensitization to hen's egg in children not previously exposed to egg ingestion.

Background: Clinical adverse reactions to egg may occur in infants or children who have never eaten egg. They may be sensitized or even react at first egg ingestion. Few studies are available concerning the reality of egg white allergy in such sensitized children, the natural evolution of this condition and the appropriate decisions to make.

Objectives: To analyze the actuality and natural course of egg allergy in children sensitized without previous of hen's egg ingestion.

Methods: We set up a clinical decision tree based on clinical history and specific egg white IgE to manage patients who had never ingested egg but were sensitized as demonstrated by a positive SPT and report a cohort of 30 such children

Results: The mean level of egg white specific IgE at first analysis, i.e. before 12 months, was high, 28.3 KU(A) /L, with a large range, from 0.6 to >100 KU(A) /L, below 6 KU(A) /L in only 8 patients. In 6 children ("no challenge" group), IgE values remained >8 KU(A) /L by the end of the survey and the oral challenge with egg was always denied. Their mean + SD IgE level was at 51.7 + 38 KU(A) /L at 1 year and 19.7 + 13 KU(A) /L at a mean age of 34 + 5 months. All had an associated anaphylactic reaction with milk and 5 were still allergic to milk by the end of the survey. In the remaining 24 infants, egg was given for the first time at a mean age of 30 + 9 months, by error in 4 cases, all exhibiting an immediate reaction, and in a hospital setting in 20, among whom 14 reacted. Among those 18, with a specific IgE level at 9.1 + 10 KU(A) /L at 28 + 9 months, 4 became tolerant between 3 and 4 years, with specific IgE levels below 1.3 KU(A) /L and a 5th one with specific IgE >100 KU(A) /L at 6 months tolerated scrambled eggs at age 7 year, with specific IgE at 2.6 KU(A) /L. In the 6 others, labeled "non allergic", egg white specific IgE levels were significantly lower, whatever the age, than in the "no challenge" group. The age at challenge was 35 + 8 months, with a mean specific IgE level at 1.0 + 0.9 KU(A) /L.

Conclusion: In children sensitized to egg without previous ingestion of that food, egg tolerance appears probably in some by the age of 3 but may reveal much more prolonged in a limited number.