Leukocytosis (increased numbers of leukocytes in the peripheral blood) is a reaction seen in many different diseasestates. The type of leukocyte that is mainly increased may be an indicator of the type of disease process present. Eosinophilia can be associated with cutaneous allergic reactions; allergic disorders, such as bronchial asthma or hay fever; Hodgkin's disease; some skin diseases, such as pemphigus, eczema, and dermatitis herpetiformis; and parasitic infections, such as trichinosis (caused by infection with trichinella spiralis), schistosomiasis, and strongyloidiasis. The most common cause of eosinophilia is probably allergy to drugs such as iodides, aspirin, or sulfonamides, but eosinophilia is also seen in collagen vascular diseases. Marked eosinophilia occurs in hypereosinophilic syndromes (Loffler's syndrome and idiopathic hypereosinophilic syndrome), which may be treated with coicosteroids. In contrast, neutrophilic leukocytosis (neutrophilia) may be the result of acute bacterial infections or tissue necrosis, such as is present with myocardial infarction, trauma, or burns. Basophilia is most commonly seen in immediate type (type I) hypersensitivity reactions. Both eosinophils and basophils may be increased in patients with any of the chronic myeloproliferative syndromes. Monocytosis is seen in chronic infections, such as tuberculosis, some collagen vascular diseases, neutropenic states, and some types of lymphomas. Lymphocytosis (especially with increased numbers of I lymphocytes) may be seen along with monocytosis in chronic inflammatory states or in acute viral infections, such as viral hepatitis or infectious mononucleosis.