The primary function of Eosinophils is to releas digestive enzymes and destroy extracellular parasites, but they also contain pro-inflammatory molecules and cytokines in their granules.
Eosinophils play an important role in late response inflammation. The primary inflammation is caused by degranulation of improper hyperactivation of mast cells when they encounter antigen/allergen (They have IgE bound to their receptors on a membrane). They release cytokines as IL-4 and IL-13 which recruit Th2 lymphocytes. Th2 lymphocytes release i.e. IL-5 which attract eosinophils.
Eosinophils release the content of their granules, which can degrade the tissue on an organism. Their cytokines attract more WBC - eosinophils (macrophages, TH2 lymphocytes and mast cells) and since this process is not controlled, they accumulate in tissues and it can lead to allergic reaction.
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