The constant progress of medical science has made it necessary to specialize on various fields. There are now many new disciplines in internal medicine and surgery.

However, some beliefs continue with little change despite this specialization. A good example to these is considering allergy first in patients with significant eosinophilia or high IgE levels.

In this article, we discuss the differential diagnosis of high IgE levels with information on the causes, when it should be investigated, and the relevant clinical findings and evaluations.