The bone marrow is where white blood cells are produced. They are kept in your blood and lymph nodes. Because certain white blood cells have a one-to-three-day lifespan, your bone marrow is constantly producing them. The older you get, the more slowly your body produces new white blood cells. When you experience a severe infection, your body creates many more white blood cells than it normally would. These extra cells help fight off the infection and sometimes cause problems for their own health: they can cause allergies, asthma, and autoimmune diseases like lupus and diabetes. After the infection has been resolved, most of the original white blood cell production returns to normal. In cancer patients, white blood cells often decrease in number. This is called leukopenia or low white blood cell count. Patients with leukemia tend to lose both neutrophils and red blood cells at a faster rate than people who have other cancers. Patients with lymphoma may only have a problem with their neutrophil count. Those with multiple myeloma may experience a reduction in all types of blood cells. While leukopenia is usually not life-threatening, it does increase the risk of infection. Cancer treatments such as chemotherapy and radiation therapy can also damage the bone marrow, preventing it from producing new cells. Long-term effects include decreased immunity against infections and increased risk of bleeding due to lack of new blood cells.