What does a high level of eosinophils indicate in a patient?

A high level of eosinophils, a type of white blood cell, typically indicates a parasitic infection. Eosinophils play a significant role in the body's defense against parasites, such as helminths (worms) and certain protozoa. They are also involved in the pathophysiology of allergy and asthma. When a parasitic infection is present, the body often responds by increasing the production of eosinophils to help combat the invaders, leading to elevated levels in the blood.

While eosinophils can also be elevated in allergic reactions and certain viral infections, the most specific association is with parasitic infections. In these cases, eosinophils help mediate the immune response and can sometimes cause tissue damage if present in high numbers. Thus, the elevation of eosinophils is a critical lab finding in the context of diagnosing parasitic infections.