Egg allergy is the most frequent food allergy in pediatric practice. Although the allergic reaction tends to decrease and even disappear with age, it can persist beyond the age of 5. However, beyond that age, some tolerate the cooked form of eggs. The purpose of the study was to evaluate the proportion of children beyond the age of 5, who while allergic to eggs, were able to tolerate cooked eggs. The usefulness of skin prick tests (SPT) to predict the outcome of cooked egg food challenge was studied.
Between January 1998 and May 2002, 60 children allergic to eggs performed an oral food challenge to cooked eggs (cake). Egg allergy was defined as an history of clinical reaction to egg with positive SPT. A prospective comparative study was conducted and two groups were observed: a first group that reacted positively to the challenge and a second group that did not.
The results showed that 73% of the egg allergic children tolerated egg in its cooked form. It was shown that the allergenicity and antigenicity of egg proteins could be altered by heat (1). The structure of the epitopes seems to play a major role in the tolerance to cooked egg. Predominance of IgE against conformational epitope, instead of linear epitope, could explain the observed tolerance to cooked egg in our population. Skin prick tests to egg white protein of ≥10 mm appears to be a strong marker to predict reaction to cooked egg challenge. The relationship between the results of SPT and the outcome of egg challenge had already been reported (2, 3) but not with cooked eggs. Also, it was shown here that presence of multiple food allergies seems to significantly increase the risk of reacting to cooked egg (Table 1).
|N (%)||16 (27%)||44 (73%)|
|Number of other food allergies||3.9||2.5||0.04|
In conclusion the persistence of egg allergy, particularly in its cooked form, seems to be associated with a stronger sensitization to specific epitopes of egg proteins and a highly atopic population. The results of both SPT and the number of other food allergies are thus factors that should be considered while deciding to subject a child to an egg oral challenge with the associated risks.