Lymphocytes are cells found in lymphatic tissue and blood, and are one of the main components of lymphatic tissue and a type of white blood cell, accounting for 20%-30% of total white blood cells, and 37%-78% of total white blood cells in infants and children. The normal absolute value of lymphocytes is (1.1-3.2) × 10^9/L. Usually, if the lymphocytes are below 20%, it is clinically referred to as low lymphocytes. Lymphocyte low is often caused by physiological decrease or pathological decrease: 1. Physiological decrease: 1. Excessive drinking: Patients who drink a lot of water, resulting in an increase in blood volume, blood dilution is prone to lymphocyte decrease, this is a normal physiological reaction, usually without special treatment, can be self-recovery relief; 2. Immunity decrease: Patients due to excessive fatigue, staying up late, irregular diet, sedentary, emotional instability This is a normal physiological reaction that usually requires no special treatment and can be remitted by itself. Pathological decrease: 1. Infectious diseases: such as typhoid fever, HIV infection, tuberculosis, etc. are also prone to lymphocyte reduction. After bacteria and viruses invade the body, they stimulate the body to release a large number of neutrophils, which leads to an increase in the ratio of neutrophils and a decrease in lymphocytes, and patients often show fever, cough, swollen lymph nodes and other manifestations. For HIV-infected people, highly effective antiretroviral combination therapy should be used, such as tenofovir, abacavir, lamivudine and other drugs; 2, immune diseases: such as rheumatoid arthritis, rheumatoid arthritis, systemic lupus erythematosus, etc. can lead to a decrease in lymphocytes, and patients often show fever, morning stiffness, joint deformities, rheumatic nodules, lymph node enlargement, skin rupture, etc. Patients often show symptoms such as fever, morning stiffness, joint deformity, rheumatic nodules, swollen lymph nodes, skin rupture, discoid erythema, etc. They can be treated with NSAIDs, slow-acting anti-rheumatic drugs, immunosuppressive drugs, etc. as prescribed by the doctor. If arthritis is more serious, surgical treatment such as release surgery, repair after tendon tear, synovectomy and arthroplasty can be performed; 3. Drug influence: If certain drugs are taken recently due to disease, which may also lead to low lymphocytes, such as chemotherapy drugs, adrenocorticotropic hormones, targeted drugs, etc., the doctor should be consulted in time to suspend the use of drugs, or to replace other drugs according to the primary disease. Avoid long-term use of such drugs, which may affect lymphocyte values; 4. Other: If long-term exposure to radiation or chemical substances may easily lead to low lymphocytes, treatment with lymphocyte-raising drugs may be used if necessary. Therefore, it is recommended that if only lymphocytes are low in the laboratory, but the white blood cell count, neutrophil percentage and hemoglobin are within the normal range, this condition is not clinically significant. In the case of low lymphocytes, it is necessary to combine the results of other tests to determine the cause of the disease and then treat the cause.