A longitudinal study of resolution of allergy to well-cooked and uncooked egg

A. Clark, S. Islam, Y. King, J. Deighton, S. Szun, K. Anagnostou and P. Ewan, Clinical & Experimental Allergy, 2011 (41) 706–712.

Background       Egg allergy is common and although resolution to uncooked egg has been demonstrated, there is lack of evidence to guide reintroduction of well-cooked egg.

Objectives       To examine the rate of resolution to well-cooked, compared with uncooked egg in children, and safety of egg challenges.

Method       A longitudinal study of egg-allergic children from 2004 to 2010, who underwent challenge with well-cooked and if negative, uncooked egg. Participants underwent repeat annual challenges and egg-specific IgE measurement.

Results       One hundred and eighty-one open egg challenges were performed in 95 children whose median age of allergy onset was 12 months. Fifty-three of 95 (56%) had at least one annual repeat challenge. Pre-study historical reactions occurred to baked egg in five (5%), lightly cooked in 58 (61%) and uncooked in nine (9%); respiratory reactions occurred in 11 (12%) and seven (7%) had anaphylaxis; adrenaline was used during five reactions. There were 77 well-cooked and 104 uncooked egg challenges. Tolerance was gained twice as rapidly to well-cooked than uncooked egg (median 5.6 vs. 10.3 years; P<0.0001) and continued to 13 years; hazard ratio 2.23 (95% confidence interval 1.6–3.9). Nearly 1/3 had resolved allergy to well-cooked egg at 3 years and 2/3 at 6 years. Of 28/77 (37%) positive well-cooked egg challenges, 65% had cutaneous symptoms, 68% gastrointestinal and 39% rhinitis, with no other respiratory reactions. Adrenaline was not required.

Conclusions and Clinical Relevance       Resolution of egg allergy takes place over many years, with children outgrowing allergy to well-cooked egg approximately twice as quickly as they outgrow allergy to uncooked egg. There were no severe reactions to well-cooked egg challenge, and adrenaline was not required. Our data support initiation of home reintroduction of well-cooked egg from 2 to 3 years of age in children with previous mild reactions and no asthma. Resolution continues to occur in older children, so that despite an earlier positive challenge, attempts at reintroduction should be continued.