About Eosinophils
Eosinophils are immune cells specialised in combating parasitic infections and orchestrating allergic responses — they release toxic proteins that kill parasites but also drive the inflammation of asthma, hay fever, eczema, and food allergy. An elevated eosinophil count (eosinophilia) is most commonly caused by allergic disease or parasitic infection in high-income countries, but very high levels (hypereosinophilia) can cause organ damage and require urgent investigation. Eosinophil count monitoring is also essential for patients taking certain asthma biologic therapies.