Which CBC finding suggests an allergic or hypersensitivity reaction?

• A. Elevation of eosinophils
• B. Elevation of neutrophils
• C. Decreased platelets
• D. Increased monocytes

Answer: (A)

Elevated eosinophils signal an allergic or hypersensitivity process because eosinophils are key players in IgE-mediated allergic responses. They are recruited to sites of allergic inflammation by cytokines like IL-5 and release mediators that contribute to symptoms seen in conditions such as allergic rhinitis, asthma, atopic dermatitis, and drug hypersensitivity. So a higher absolute eosinophil count on a CBC is a clue that an allergic reaction may be involved.

Neutrophils, by contrast, rise mainly with acute bacterial infections or general inflammation; platelets that are low point to a thrombocytopenic process; and monocytes tend to be elevated in chronic inflammatory states or certain infections. Those patterns fit different clinical pictures, not the classic allergic reaction.