It's possible to have a higher than usual lymphocyte count but have few, if any, symptoms. The higher count usually comes after an illness. It is most often harmless and doesn't last long.

But the higher count might be the result of something more serious, such as a blood cancer or a chronic infection. More tests can show if the lymphocyte count is a cause for worry.

A high lymphocyte count can point to:

1. Infection, including bacterial, viral or other type of infection.
2. Cancer of the blood or lymphatic system.
3. An autoimmune disease causing ongoing, called chronic, swelling and irritation, called inflammation.

Causes of lymphocytosis include:

1. Acute lymphocytic leukemia
2. Babesiosis
3. Brucellosis
4. Cat-scratch disease
5. Chronic lymphocytic leukemia
6. Cytomegalovirus (CMV) infection
7. Hepatitis A
8. Hepatitis B
9. Hepatitis C
10. HIV/AIDS
11. Hypothyroidism (underactive thyroid)
12. Lymphoma
13. Mononucleosis
14. Severe medical stress, such as from trauma
15. Smoking
16. Splenectomy
17. Syphilis
18. Toxoplasmosis
19. Tuberculosis
20. Whooping cough