Although mast cells are primarily implicated, basophil involvement in HαT remains poorly defined.<h4>Objective</h4>Our aim was to compare basophil proportions, MRGPRX2 expression, and responsiveness to IgE-dependent and IgE-independent activation in individuals with HαT, individuals with indolent systemic mastocytosis (ISM), and healthy controls (HCs).<h4>Methods</h4>Peripheral blood was obtained from individuals with HαT (n = 20), individuals with ISM (n = 31), and HCs (n = 8). Here, MRGPRX2 is linked to systemic mastocytosis.