White blood cells are disease-fighting cells that scavenge the blood stream for bacteria, viruses and other foreign particles. Certain medical conditions can cause white blood cell levels to rise, specifically a condition called leukocytosis, which itself is not considered a disease. White blood cell levels are typically measured through lab tests in the diagnosis of illness or infection.
Infection
White blood cells are produced by the bone marrow to fight off potential threats of infection. The Mayo Clinic explains that during times of infection or inflammation, the body will produce more white blood cells than when the body is healthy.
Drugs
Certain drugs have immune-related side effects that lead to increased white cell production. The American Academy of Family Physicians lists medications that may have leukocytic side effects, including corticosteroids, lithium and beta-agonists.
Bone Marrow Diseases
Certain diseases of the bone marrow can cause an increase in white cell production. The most common diseases of the bone marrow associated with high white blood cell counts are leukemia and lymphoma. The Merck Manual explains that leukocytosis will lead to the overproduction of abnormal white cells whereas leukocytosis from infection will produce normal white blood cells.
Immune System Disorders
Disorders of the immune system can result in an increased production of white cells. According to the Merck Manual, high white counts can occur in response to Graves' disease or Crohn's disease. Graves' disease occurs when the immune system attacks the thyroid gland, leading to a number of hormonal changes that can affect the body in a variety of ways, including leukocytosis. Crohn's disease is an inflammatory disease of the bowel or digestive tract that may occur as an abnormal immune response to certain infections.
Physical or Emotional Stress
According to the American Academy of Family Physicians, stress can also be a cause of high white blood cell counts. This is a very transient condition that is not related to marrow production and subsides as soon as the underlying stress is resolved. Such causes of leukocytosis can include seizures, anxiety, overexertion and anesthesia or epinephrine administration.
Splenectomy
Certain immune disorders of the blood may require the removal of the spleen. The American Academy of Family Physicians explains that a splenectomy can result in high white blood cell counts in the weeks following surgery.
