There is a striking relationship between eosinophilia and allergenic exposure among atopic patients, and the existence of eosinophilia is an indication of such exposure. The term "eosinophilosis" is suggested as an appropriate descriptive designation embracing all patients with atopic manifestations whether or not specific allergic causes are recognizable. There are many advantages to the total eosinophil count (TEC) in diagnosis and in the assessment of response to treatment with steroids.
Lowell FC. Clinical Aspects of Eosinophilia in Atopic Disease. JAMA. 1967;202(9):875-878. doi:10.1001/jama.1967.03130220063010