High Eosinophils (Eosinophilia): What Does It Mean? When to worry?

Under normal conditions, these cells represent approximately 1-4% of the leukocyte population in peripheral blood, expressed as an absolute value: 100-500 eosinophils / μl (per microliter of blood). On the other hand, their concentration in those tissues exposed to environmental agents, such as the mucous membranes of the digestive tract and respiratory tract, the genitourinary epithelia and the skin connective tissue, is higher. At this level, in fact, eosinophils protect the body from any attack by parasites, which fight by releasing substances capable of damaging or killing them.

Blood eosinophil counts vary with age, time of day (low in the morning, higher in the evening), physical exercise, environmental stimuli and, in particular, allergenic exposure.

Their number can increase markedly in the course of many diseases, in particular in parasitic infestations and allergic reactions: this phenomenon is called eosinophilia. Instead, we speak of eosinopenia to indicate the decrease, which is observed in the acute phase of some infectious diseases, in anaphylactic shock and after administration of corticosteroids.