A recent article by Lawrence Afrin (international expert on Mast Cell Activation), has suggested that Mast Cell Activation may be a mediator of Long COVID syndrome (multiple persistent and debilitating symptoms following a COVID-19 infection) and many Long COVID symptoms mimic those of Mast Cell Activation (including unexplained rashes and swelling, confusion with fatigue, palpitations, POTS syndrome, Fibromyalgia, nausea and headaches).
Reference: https://www.sciencedirect.com/science/article/pii/S1201971221007517
