Anaphylaxis is a serious systemic hypersensitivity reaction that develops within minutes after exposure to a specific allergen. Serum tryptase concentration is the most used laboratory test to confirm the clinical diagnosis of anaphylaxis. A biomarker that would allow an unambiguous diagnosis of anaphylaxis is still not recognized. Previous research has shown that cytokine oncostatin M (OSM), matrix metalloproteinase 9 (MMP9) and interleukin 1 type II receptor (IL1R2) could play an important role in biological processes during anaphylaxis. For this reason, we designed a study where we measured the relative mRNA expression of IL1R2, MMP9 and OSM genes in the blood of patients during anaphylaxis using real-time polymerase chain reaction (RT-qPCR). The mRNA expression of selected genes increased during the acute phase of anaphylaxis. ROC curves showed that the sensitivity and specificity of the designed diagnostic tests are even better than tryptase. For experimental comparison, peripheral mononuclear cells (PMNCs) were isolated from the blood of patients with confirmed hypersensitivity to bee or wasp venom, in vitro stimulated with an allergen, and mRNA expression of the aforementioned genes was measured.