Long‐term changes in milk component immunoglobulins reflect milk oral immunotherapy outcomes in Finnish children

BACKGROUND: Milk oral immunotherapy (OIT) may increase the amount of milk protein that can be ingested without triggering an allergic reaction. It is important to understand why some patients benefit from the treatment while others do not. OBJECTIVE: The aim was to define the differences in the milk allergen component‐specific (casein, α‐lactalbumin, ß‐lactoglobulin) immunoglobulin (sIg [sIgE, sIgG4, and sIgA]) levels relative to the long‐term outcomes of milk OIT. METHODS: In this long‐term, open‐label follow‐up study, 286 children started milk OIT between 2005 and 2015. Follow‐up data were collected at two points: the post‐buildup phase and long term (range 1–11 years, median 6 years). Comparisons of sIg levels were made among three outcome groups of self‐reported long‐term milk consumption (high‐milk dose, low‐milk dose, and avoidance). RESULTS: A total of 168 (59%) of the 286 patients on OIT participated. Most patients (57%) were in the high‐dose group; here, 80% of these patients had a baseline casein sIgE value less than 28 kUA/L, they had the lowest casein sIgE levels at all time (p < .001), their casein sIgG4/IgE levels increased, and long‐term casein sIgA was highest compared with the low‐dose and avoidance groups (p = .02). Low‐milk dose group had the highest casein sIgG4/IgE levels in long term (p = .002). CONCLUSION: The baseline Ig profiles and responses to milk OIT differed depending on long‐term milk consumption. Lower casein sIgE levels were associated with better outcome. Milk casein sIgA differed in the long term among high‐milk consumers.