RT Book, Section A1 Ujiie, Hideyuki A1 Shimizu, Hiroshi A2 Kang, Sewon A2 Amagai, Masayuki A2 Bruckner, Anna L. A2 Enk, Alexander H. A2 Margolis, David J. A2 McMichael, Amy J. A2 Orringer, Jeffrey S. SR Print(0) ID 1161329698 T1 Eosinophilic Diseases T2 Fitzpatrick's Dermatology, 9e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9780071837798 LK dermatology.mhmedical.com/content.aspx?aid=1161329698 RD 2024/10/11 AB AT-A-GLANCEEosinophils are bone marrow–derived cells that circulate transiently and normally account for up to 6% (up to 600/mm3) of circulating blood leukocytes.Eosinophils primarily are tissue-dwelling cells, but only in certain tissues in humans, with an average tissue life span of 2 to 5 days that may be increased with eosinophil survival factors for up to 14 days.As proinflammatory cells, the presence of eosinophils within most tissues is associated with pathologic states that include infections, allergic reactions and atopic diseases, fibrotic disorders, reactive eosinophilias, and hypereosinophilic syndromes.Eosinophils play a role in innate and adaptive immune responses, which may explain why they are present in normal, noninflamed tissues such as the gastrointestinal tract and lymphoid tissues.This section reviews the biologic actions of eosinophils with particular focus on what controls eosinophil production, activation, and tissue trafficking.Pharmacologic manipulation of eosinophil inflammation is possible as new, more specific strategies are emerging.