Tryptase and histamine may support oral food challenge in the diagnosis of allergy

Allergen-specific immunoglobulin E (IgE) reactions lead to acute degranulation of mast cells and basophils and release of stored mediators, particularly tryptase and histamine, which can be measured in vitro after reactions. The aim of this study was to investigate the utility of serum tryptase and plasma histamine during oral food challenge (OFC) in 103 children with suspected food allergy, in order to support the diagnosis of a IgE-mediated reaction. Blood samples for serum tryptase and plasma histamine were collected before the OFC and after the onset of allergic symptoms or after 60 minutes from test completion. Serum tryptase and plasma histamine were measured by a fluoroenzyme immunoassay (ImmunoCAP; ThermoFisher, Uppsala, Sweden) according to the manufacturer’s instructions. A correlation between serum tryptase and plasma histamine distributions was observed after OFC (p=0.0035). A correlation was also observed for both serum tryptase and plasma histamine before and after OFC (p less than0.0001). Subjects with positive response to OFC had significantly higher values (p = 0.0375) of serum tryptase compared to subjects with negative response. The plasma histamine distribution showed a significant difference between measurements before and after OFC, both in the complete population (p less than 0.0001), and considering the response (negative OFC: p less than 0.0001; positive OFC: p=0.0181). The diagnostic work-up of IgE- mediated food allergy may include determination of serum tryptase and plasma histamine, in order to support the results of OFC. These markers are strongly related to the same IgE-mediated mechanism and, as they can be both easily measured, can confirm the allergic nature of a reaction in the real-life setting of food allergy.