for asthma driven by eosinophils. it's designed to target and remove them and helps prevent asthma attacks. fasenra is not for sudden breathing problems or other eosinophilic conditions. allergic reactions may occur. don't stop your asthma treatments without talking with your doctor. tell your doctor if your asthma worsens. headache and sore throat may occur. tell your doctor if you have a parasitic infection. get back to better breathing. ask your doctor about fasenra.