Neutrophils are a type of white blood cells, which protect the body against infectious agents by migrating toward the source of irritation. Neutrophilia refers to a higher than normal number of neutrophils for age or sex of the individual. The increase in their number may be a result of a shift of cells from the capillaries and organs to the blood (shift neutrophilia) or from a true increase in their number caused by increased production (true neutrophilia). Shift neutrophilia is usually transient, may occur in association with vigorous exercise or stress (following meals, pregnancy, smoking, seizures or tachycardia) and usually lasts 20-30 minutes. True neutrophilia is usually related to infections and leads to increased production of cells in the marrow. If the demand of cells is high, immature neutrophils escape from the marrow into the blood (called a shift to the left in the differential count). Neutrophilia can occur from
Acute infections caused by bacteria (staphylococci, pneumococci, streptococci, meningococci, gonococci, Escherichia coli, Pseudomonas aeruginosa, Actinomyces species); certain fungi (Coccidioides immitis); spirochetes; viruses (rabies, poliomyelitis, herpes zoster, small pox, varicella); rickettsia; and parasites (liver fluke)
Non-infectious inflammatory states (like burns, post-operative state, acute myocardial infarction, acute attacks of gout, acute glomerulonephritis, intestinal obstruction, strangulated hernia, rheumatic fever, collagen vascular diseases, hypersensitivity reactions)
Metabolic states (diabetic ketoacidosis, pre-eclampsia, uraemia)
Poisoning
Acute haemorrhage (into body spaces such as the peritoneal cavity, pleural cavity, joint cavity, intracranial space
Myeloproliferative disorders (chronic myeloid leukaemia, polycythaemia vera, myelofibrosis, myeloid metaplasia)
Malignant tumours
Medications like acute or chronic administration of corticosteroids
Chronic idiopathic neutrophilia and Hereditary neutrophilia - neutrophilia present without an identifiable cause. As you can see the list of causes is large. You need a meticulous clinical examination followed by relevant investigations so that appropriate treatment can be instituted. It is important to remember that one treats an individual and not an abnormal test result.