Safety of Oral Food Challenges for Individuals with Low Levels of Cow's Milk-Specific Immunoglobulin E Antibodies.

Introduction: Cow's milk (CM) is one of the most common food allergens in Japan. The oral food challenge (OFC) of CM is important for the definite diagnosis of children with CM allergy and it is recommended to be actively and safely performed in individuals with low CM-sIgE levels. This study aimed to investigate the safety of low-dose CM-OFC in individuals with low CM-sIgE levels and discuss the prognostic factors and appropriate approaches for assessing the starting doses of CM-OFC in these individuals.

Methods: We retrospectively analyzed 6,929 OFC tests conducted between January 1, 2017 and December 31, 2021; of which, 1,390 were CM-OFC tests. The characteristics, OFC-positive rates, CM loading, and related factors were analyzed in 138 cases involving low CM-sIgE levels. Stepwise OFC tests were conducted according to the FA guidelines in Japan using an open and unblinded method.

Results: Among 138 individuals with low CM-sIgE levels, 110 (79.7%) passed the OFC test without any symptoms. Among the cases with OFC-positive status, 50.0% (14/28) cases showed symptoms with low-dose OFC (30-105 mg CM protein). Moreover, complete CM elimination was associated with a significantly high OFC-positive rate, and 60.0% (12/20) of the cases involving complete CM elimination showed symptoms with low-dose OFC.

Conclusion: Eighty percent of the patients with low CM-sIgE levels safely completed the OFC test. Nevertheless, careful observation is essential during low-dose OFC test in cases with low CM-sIgE levels, especially in the cases with complete elimination. The starting dose of the OFC test should be re-evaluated and modified using baked milk or a lower dose of CM to ensure safety and early outgrowth of CM allergy.