Eosinophils are a type of white blood cell that play an important role in the immune system's response to parasitic infections and allergic reactions. Synonyms for eosinophil include eosinophil granulocyte, acidophil, and oxyphil. These terms all refer to the same type of white blood cell that contains granules filled with acidic proteins, which give them a distinct red-orange color when stained with certain dyes. In addition to their role in fighting parasitic infections and allergic reactions, eosinophils have been implicated in a variety of other disease processes, including asthma, inflammatory bowel disease, and certain types of cancer. Understanding the function and significance of eosinophils can be important in the diagnosis and treatment of these conditions.