The Eosinophil (EOS) test is a blood test performed as part of a complete blood count (CBC) to measure the level of eosinophils in the blood. Eosinophils are a type of white blood cell that plays a key role in the body's defense, particularly against allergic reactions and parasitic infections. The main purposes and conditions for which this test is used include:

* Diagnosis and monitoring of allergic diseases such as allergic rhinitis and atopic dermatitis.
* Detection of parasitic infections.
* Assessment of autoimmune disorders affecting the immune system.
* Assisting in the diagnosis and monitoring the progression of certain types of cancers, such as lymphoma and leukemia.