Hi! Thank you for posting your query in Healthcaremagic. Eosinophilia is a higher than normal level of eosinophils. A count of more than 500 eosinophils per microliter of blood is generally considered eosinophilia in adults. A count of more than 1,500 eosinophils per microliter of blood that lasts for several months is called hypereosinophilic syndrome Most common cause would be: -Allergy (Allergic rhinitis, Alleric to dust ,pollen,cold air ,etc) - Parasictic and fungal Disease – like Ascarasis , Trichinosis (roundworm Infection),Filariasis -Asthma - Atopic dermatitis (eczema) -Hay fever -Lymphomas -Also seen in tumors -Sometimes, cause is unknown (Idiopathic hypereosinophilic syndrome (HES) Treatment will depend on the cause that is leading to elevated eosinophil counts. As per Information provided ,you have mentioned that all reports are normal. In your case,Mild headache persisting for more than 3 weeks ,need to know if any additional problems with Headache ( Running nose,sneezing ,fever ,itching of the skin,history of sinusitis etc) Request to update the history for further advice .Also kindly need to see the tests that done along with reports for further advice and opinion I hope that I have answered your questions fully and been of some help. Regards, Dr.Sushma