Lymphocytosis often results from your immune system fighting off an infection or other disease. White blood cells called lymphocytes increase with these conditions. Lymphocytosis isn’t preventable, but it can be treated by addressing what’s causing your temporary high lymphocyte count.

Causes of Lymphocytosis


Lymphocytosis often results from viral infections. Bacteria and parasites can also cause infection, resulting in a high lymphocyte count. Infectious causes of lymphocytosis include:

  • Epstein-Barr virus (the virus that causes mononucleosis).

  • Cytomegalovirus (CMV).

  • Influenza (the flu).

  • Whooping cough.

  • Adenovirus.

  • Hepatitis.

  • Chickenpox or shingles.

  • Mumps.

  • Rubella.

  • HIV.


In some cases, lymphocytosis is one of the first signs of certain blood cancers (leukemia) or cancers of your lymphatic system (lymphoma). Cancers associated with lymphocytosis include:

  • Chronic lymphocytic leukemia.

  • Non-Hodgkin lymphoma.

  • Acute lymphoblastic leukemia.

  • Large granular lymphocyte leukemia.

Other causes

  • Smoking.

  • Allergic reaction to medicine.

  • Stress related to a medical emergency.

  • Some autoimmune diseases.

  • Asplenia (removal of your spleen).

Symptoms of Lymphocytosis

  • Lymphocytosis doesn’t cause symptoms. However, you may experience symptoms from what’s causing the spike in your white blood cell count.

  • For instance, the lymph nodes in your neck may feel swollen due to an infection, which may be causing lymphocytosis.

  • Depending on the cause, symptoms may range from no symptoms to severe.

  • Often, people learn of a high lymphocyte count incidentally after taking a blood test to check for other conditions.

Diagnosis of Lymphocytosis

  • Your provider may order a blood test called a complete blood count (CBC) with differential.

  • This test shows if you have a higher-than-normal amount of lymphocytes.

  • They may order a flow cytometry test to see if the lymphocytes are clonal (seen in cancers like chronic lymphocytic leukemia).

  • Testing may also include a bone marrow biopsy to help determine the root cause of lymphocytosis.

Treatment of Lymphocytosis

  • Lymphocytosis treatment involves resolving what’s causing the high lymphocyte count.

  • If your body is producing white blood cells to fight a germ, you may not need treatment.

  • In time, your immune system can usually take care of the issue.

  • If the spike in white blood cells is a sign of cancer, you can discuss treatment options with your provider.

  • Receiving treatment for the underlying cause can help restore your lymphocyte levels to normal.

diseases treatments health disorders prevention lymphatic-system

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