White blood cells play an important role in the immune system as they scavenge the blood for invading viruses, bacteria and fungi. Individuals with a high white blood cell count, a condition called leukocytosis, typically do not present with any specific symptoms but may have an unknown medical condition responsible for raising white cell levels. If your doctor discovers your white cell levels have become high, they may perform additional tests to look for a potentially dangerous, underlying condition.
Infection
Infection is a common reason for elevated white blood cell levels. The Mayo Clinic explains that as bacteria and viruses multiply in the blood, the bone marrow will produce more white blood cells to battle the infection. Infection can also cause inflammation which also leads to increased white blood cell levels.
Smoking and Chronic Obstructive Pulmonary Disease (COPD)
The National Heart Lung and Blood Institute describes COPD as a collection of lung and airway diseases which block proper airflow. COPD includes emphysema and chronic bronchitis. COPD commonly results from cigarette smoking which causes inflammation in the lungs and airways. As the lungs and airways become inflamed, the body will produce more white blood cells which recruit to the lungs, further restricting the airway.
Leukemia
Leukemia is a cancer of the white cell producing cells in the bone marrow that leads to a dramatic increase in white cell levels. The Mayo Clinic explains that leukemic white blood cells are typically non-functional and that leukemia patients then become susceptible to infection. Nonetheless, a high white blood cell count may include such non-functional white cells and may indicate leukemia or another cancer of the blood or bone marrow.
Immune System Disorders
Some auto-immune system disorders can cause and increase white blood cell production. The Merck Manual explains that Graves' disease and Crohn's disease can elevate white blood cell levels. Crohn's disease is an auto-immune disease of the digestive tract that causes bowel inflammation. Graves' disease is an auto-immune disease of the thyroid gland that causes hormonal fluctuations that can cause the bone marrow to produce more white cells.
Stress
According to the American Academy of Family Physicians, physical or emotional stress can cause high white blood cell counts. Leukocytosis from stress is a transient condition that is not directly related to marrow production. White cell levels will typically resolve to normal levels once an underlying stress is eliminated. Stresses related to leukocytosis include seizures, anxiety, overexertion and anesthesia or epinephrine administration.
