Wechsler et al., 2022 assessed levels of mast cell-derived proteases to evaluate mast cell activation in symptomatic PASC patients. Active tryptase levels were significantly elevated in PASC sera compared to asymptomatic post-COVID patients and heathy controls. Serum tryptase levels also correlated with IL-6 levels in the PASC patients. The importance for PASC patients relates to current pharmacological strategies such as antihistamines to treat MCAS, and their potential application in PASC (Davis et al., 2023). This evidence concerns the gene IL6 and long COVID-19.