Causes of lymphocytosis (Increased Lymphocytes) (> 4000/cumm in adults, > 7200/cumm adolescents, > 9000/cumm in children and infants)

Causes of lymphocytosis (> 4000/cumm in adults, > 7200/cumm adolescents, > 9000/cumm in children and infants)

Infection (Pertusis, infectious, lymphocytosis, infectious hepatitis, cytomegalovirus (CMV) infections, mumps, rubella, varicella, toxoplasmosis, chronic tuberculosis), 

Others like 

thyrotoxicosis,

Addison's disease, 

neutropenia with relative lymphocytosis, 

lymphatic leukemia, 

Crohn's disease, 

ulcerative colitis and 

infancy (normal count 40- 60 %) called relative lymphocytosis.