Eosinophil

Eosinophils are white blood cells that are responsible for combatting infection by parasites that enter the bloodstream.

These cells, transparent in vivo, appear brick-red when stained by the Romanowsky method. The red colour is visible as small granules within the cell. These granules contain histamine[?], and other chemicals that are toxic to both parasites and the host's tissues.

Eosinophils also play a role in the allergic response, and in fibrin removal in inflammation.

An increase in eosinophils is called an eosinophilia, and is typically seen in people with a parasitic infection of the intestines.