Oral immunotherapy (OIT) induces desensitization and/or tolerance in patients with persistent food allergy, but the biomarkers of clinical outcomes remain obscure. Although OIT‐induced changes in serum allergen‐specific IgE and IgG4 levels have been investigated, the response of other allergen‐specific IgG subclasses and IgA during OIT remains obscure.

A pilot study was conducted to investigate egg OIT‐induced changes in allergen‐specific IgE, IgG subclasses, and IgA levels and search for possible prediction biomarkers of desensitization. We measured serum levels of egg white‐, ovomucoid‐, and ovalbumin‐specific IgE, IgA, and IgG subclasses by high‐sensitivity allergen microarray in 26 children with egg allergy who received rush OIT.

Allergen‐specific IgE gradually decreased while IgG4 increased during 12‐month OIT. Serum levels of IgG1, IgG3, and IgA increased significantly after the rush phase, then decreased during the maintenance phase. IgG2 levels changed in a manner similar to that of IgG4. In particular, significantly high fold increases in egg white‐specific IgG1, relative to baseline, after the rush phase and high IgA levels before OIT were observed in responders, compared with low‐responders to OIT. Patients who could not keep desensitization showed relatively small changes in all immunoglobulin levels during OIT.

The response to OIT was associated with significant increases in serum allergen‐specific IgG1 levels after rush phase and high baseline IgA levels, compared with small changes in immunoglobulin response in low‐responders. The characteristic IgG1 changes and IgA levels in the responders could be potentially useful biomarkers for the prediction of positive clinical response to OIT.