What are eosinophils ?
Components of blood 
Eosinophils are WBCs. And they are the components of the blood .
The Normal range 1-6%(0.02-0.5 × 10^9/L)
How does it help the human body ?
What causes eosinophilia ?
If eosinophil count is more that 450/cu mm
Causes –
Drug reaction seen in eosinophilia 
Source- textbook of pathology for dental students Ramdas Nayak , Wikipedia