Which laboratory finding indicates an allergic response is in progress?

Which laboratory finding indicates an allergic response is in progress?

• A. Decreased platelet count
• B. Increased lymphocyte count
• C. Decreased immunoglobulin level
• D. Increased eosinophil level

Answer: (D)

An allergic response involves a Th2-driven inflammatory process that recruits eosinophils to sites of exposure. Eosinophils respond to cytokines like IL-5, increasing in number as part of ongoing allergic inflammation. Therefore, an elevated eosinophil count is the lab finding that best signals an active allergic process, such as in atopy or asthma. The other options don’t fit as well: a decreased platelet count isn’t characteristic of allergy and points more to hematologic or systemic issues; an increased lymphocyte count is more typical of viral infections or chronic immune activation; a decreased immunoglobulin level indicates immunodeficiency rather than an active allergic reaction.

An allergic response involves a Th2-driven inflammatory process that recruits eosinophils to sites of exposure. Eosinophils respond to cytokines like IL-5, increasing in number as part of ongoing allergic inflammation. Therefore, an elevated eosinophil count is the lab finding that best signals an active allergic process, such as in atopy or asthma.

The other options don’t fit as well: a decreased platelet count isn’t characteristic of allergy and points more to hematologic or systemic issues; an increased lymphocyte count is more typical of viral infections or chronic immune activation; a decreased immunoglobulin level indicates immunodeficiency rather than an active allergic reaction.