Serum levels are normally less than ng/mL.  Elevated levels of serum tryptase occur in both anaphylactic and anaphylactoid reactions, but a negative test does not exclude anaphylaxis . Tryptase is less likely to be elevated in food allergy reactions as opposed to other causes of anaphylaxis. Serum typtase levels are also elevated in and used as one indication suggesting the presence of eosinophilic leukemias due to genetic mutations resulting in the formation of FIP1L1-PDGFRA fusion genes or the presence of systemic mastocytosis .  
Calcium triggers the secretion of histamine from mast cells after previous exposure to sodium fluoride. The secretory process can be divided into a fluoride-activation step and a calcium-induced secretory step. It was observed that the fluoride-activation step is accompanied by an elevation of cyclic adenosine monophosphate (cAMP) levels within the cells. The attained high levels of cAMP persist during histamine release. It was further found that catecholamines do not markedly alter the fluoride-induced histamine release. It was also confirmed that the second, but not the first, step in sodium fluoride-induced histamine secretion is inhibited by theophylline.  Vasodilation and increased permeability of capillaries are a result of both H1 and H2 receptor types.