An eosinophil chemotactic factor (ECF) can be released from human polymorphonuclear neutrophils (PMN), rat mononuclear and rat mast cells by the calcium ionophore, during phagocytosis, by arachidonic acid and phospholipase A₂. It has been suggested that stimuli such as the ionophore and the phagocytic event lead to phospholipid turnover with the generation of arachidonic acid which is subsequently transformed by a lipoxygenase-like enzyme into ECF. 

Chemokine (C-C motif) ligand 11 (CCL11) is a small cytokine belonging to the CC chemokine family that is also known as eotaxin-1. CCL11 selectively recruits eosinophils by inducing their chemotaxis, and therefore, is implicated in allergic responses.