Allergy-Related Eosinophilia in Children

Eosinophilia (an increased eosinophil count) can be found both in the peripheral blood and in tissues in several medical conditions. The most frequent causes of blood and tissue eosinophilia include atopic diseases, parasitic infections, malignancies, immunodeficiency, and vasculitis. A careful history and physical examination along with directed clinical evaluation may help determine the cause. Allergic diseases are characterized by type-2 eosinophilic inflammation and are usually associated with mild eosinophilia in the bloodstream (<1500 cells/microliter). This chapter focuses on allergy-related eosinophilia and highlights how eosinophilic inflammation contributes to the pathogenesis of allergic rhinitis, asthma, atopic dermatitis, and eosinophilic gastrointestinal disorders.