Eosinophils are a type of white blood cell that play a crucial role in the immune system. They are primarily involved in combating parasitic infections and are also important in allergic reactions. Eosinophils contain granules filled with enzymes and proteins that can help destroy pathogens and modulate inflammation. These cells are produced in the bone marrow and circulate in the bloodstream. When there is an infection or an allergic response, eosinophils migrate to the affected tissues. Elevated levels of eosinophils can indicate conditions such as asthma, allergies, or parasitic infections.