Patients displaying eosinophilia overexpress a gene encoding an eosinophil hematopoietin. High concentrations of eosinophil granulocytes are in blood. The eotaxins are a CC chemokine subfamily of eosinophil chemotactic proteins. Other cells activated by CD28 ligation in humans are eosinophil granulocytes. Cetirizine has been shown to inhibit eosinophil chemotaxis and LTB4 release. Approximately 1/3 of cases exhibit increases in blood eosinophil counts, either eosinophilia or hypereosinophilia. An absolute eosinophil count is not generally needed if the CBC shows marked eosinophilia. Until recently, peripheral eosinophilia (high eosinophil counts) was considered partly indicative of ABPA. However, as a case of eosinophilic meningitis progresses, intracranial pressure and eosinophil counts should rise. Anti-cholinergics, decongestants, and other compounds thought to impair eosinophil chemotaxis, are also commonly used. Specific deficiency of eosinophil peroxidase without concomitant deficiency of myeloperoxidase is rare. Major basic protein, eosinophil peroxidase, and eosinophil cationic protein are toxic to many tissues. Scanning for white blood cells can help diagnose eosinophil esophagitis. The promoter sequence for human eosinophil peroxidase is an unusually strong promoter. PRG2 is a 117-residue protein that predominates in eosinophil granules.