Which white blood cell is most associated with allergic reactions and parasitic infections?

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Eosinophils are the white blood cells most closely tied to allergic reactions and parasitic infections. They are drawn to sites of parasitic invasion and are activated by IL-5 from Th2 cells, expanding in number during these conditions. Their granules contain toxic proteins, such as major basic protein, that can directly attack parasites and also amplify inflammatory responses seen in allergies. In allergic settings, eosinophils contribute to tissue damage and prolonged inflammation, helping to sustain the reaction. Basophils mainly release histamine in IgE-mediated immediate hypersensitivity but aren’t the primary defense against parasites. Neutrophils handle bacterial infections and acute inflammation, while lymphocytes drive adaptive immunity and are not specialized for parasites or allergy in the same way.