Eosinophils are typically elevated in which conditions?

• A. Allergic reactions
• B. Bacterial infections
• C. Viral infections
• D. Iron deficiency anemia

Answer: (B)

Eosinophils rise most with allergic reactions because they are central to type 2 immune responses. In allergies, Th2 cells release IL-5, which stimulates the bone marrow to produce more eosinophils and guides their migration to inflamed tissues. There, eosinophils release mediators that amplify inflammation and can contribute to symptoms like itching, swelling, and tissue damage. In contrast, bacterial infections typically cause a neutrophil-dominant response, viral infections tend to boost lymphocytes, and iron deficiency anemia does not drive eosinophil production. So allergic reactions best explain why eosinophils are elevated.