Children with Delayed-Type Cow's Milk Protein Allergy May Be at a Significant Risk of Developing Immediate Allergic Reactions Upon Re-introduction.

Background: Cow's Milk Protein Allergy (CMPA) is the most common food allergy in children. The reaction is classified into IgE-mediated immediate reaction and delayed-onset, according to the underlying immune mechanism, and hence, the timing of the symptoms. Case reports suggest that children, with delayed CMPA reactions on elimination diet, may develop severe immediate reactions on reintroduction. Aim: The objective of this study was to evaluate the incidence and the risk factors of developing immediate reactions to milk and dairy products in children with CMPA whose initial presentations were of delayed type. Methods: A retrospective chart review of children, aged 0-12 years, presented with delayed type CMPA reactions to the allergy-clinical immunology clinics, was performed. The diagnosis was made clinically, and with appropriate allergy tests when indicated. Results: Sixty children were included. Males:female ratio was 1.7:1. Family history of atopy was in 72%, and 57% had personal history of atopy. Sixty percent were not breast fed. The most common concomitant food allergy was egg. The most common initial presentation was diarrhea without protein loss or bleeding followed by exacerbation of atopic dermatitis upon exposure to dairy products. Immediate reactions developed in 21.6% upon re-exposure. There were significant associations with concomitant food allergy (OR 56.6 (3.15-1016.1) P<0.0001), especially eggs (OR 12.85 (3.09-53.5) P<0.01). Conclusion: Children with CMPA, who present with delayed-type allergic reactions, may be at a significant risk of developing immediate reactions upon reintroduction. Evaluation of possible IgE-mediated allergic reactions before reintroduction may be advisable.