Serum Diamine Oxidase Levels in Relation to Skin Prick Testing and Specific IgE in Adults with Self-Reported Food Allergy.

Self-reported food allergy is a common concern among adults and often prompts the use of diagnostic allergy testing. However, serum diamine oxidase (DAO) measurement is rarely performed, despite the fact that symptoms of histamine intolerance can closely mimic those of IgE-mediated food allergy. This study aimed to analyze and compare the results of commonly used food allergy tests in relation to serum DAO levels in this patient population. A total of 61 adult patients with self-reported food-related symptoms were enrolled. All participants underwent skin prick testing and serum DAO measurement using an enzyme-linked immunosorbent assay (ELISA). In addition, serum-specific IgE (sIgE) testing was performed in 29 of the 61 patients. DAO levels were compared across groups based on skin prick testing and sIgE results. Fewer than half of the patients had positive test results, 36% for skin prick testing and 38% for sIgE, and 38% showed reduced serum DAO levels. DAO levels did not differ significantly between patients with positive and negative skin prick or sIgE results; however, a slight decrease in DAO was observed in patients with negative sIgE. Patients with negative skin prick tests were significantly older than those with positive results. The majority of adults with self-reported food allergies had negative allergy test results and normal DAO levels. Nevertheless, a considerable proportion showed either positive allergy tests or reduced DAO levels, suggesting the potential role of histamine intolerance. These findings underscore the importance of a detailed pre-test clinical assessment that considers both IgE- and non-IgE-mediated mechanisms in patients with suspected food-related hypersensitivity.