The agreement between reported allergies and positive IgE (considered to be an IgE concentration ≥ 25 UI/ml) was weak in all groups: κ = 0.000 in the control group, κ = 0.002 in the cancer patient group, namely κ = −0.037 for prostate adenocarcinoma, κ = 0.237 for gastric adenocarcinoma, and κ = −0.250 for HNSCC. Here, IGHE is linked to head and neck squamous cell carcinoma.