As expected, when compared to patients without allergy, SIgAD patients with allergy had higher IgE serum levels (33 UI/mL (IQR 14–55) vs. 474 UI/mL (IQR 49–1119), p = 0.018), whereas they did not have lower IgG, IgA, IgM, or IgG subclass serum levels either at diagnosis or during FU. Here, CD40LG is linked to Allergy.