ha several cause. I wish you must have added your symptomatology.
usual causes are, Total peripheral eosinophilia(TPE) due to filariasis, loeffler's syndrome ( due to passage of worms like ascariasis through lungs), allergic phenomenon, ABPA ( asthma complicated by mould aspergillus
), hypereosinophilic syndrome
(when no cause is detected and absolute eosinophil count
is persistently above 1500 for 6 months), churgh strauss syndrome ( a vasculitis which involves the small vessels of the body) etc....
hope you will have your diagnosis made when you meet your doctor