Upper extremity edema is one of the most common complications in patients who have undergone axillary lymph node dissection for breast cancer, with an incidence of approximately 6% to 14% reported in the literature. It is generally considered as severe edema when the circumference of the affected upper extremity is <3 5="">5 cm longer than the circumference of the contralateral upper extremity in the same position. What should be done to prevent or reduce upper limb edema in these patients? (1) Prevent infection: keep the skin on the affected side clean; do not perform invasive operations on the affected arm, such as blood sampling, infusion, blood pressure measurement, etc.; wear loose gloves when washing clothes and avoid prolonged contact with irritating washing solutions; avoid mosquito bites; dress, wear jewelry or watches in a loose manner. (2) Avoid high temperature environment: avoid burns; do not apply hot compresses to the affected arm, do not overheat the water when bathing; avoid bright light exposure and high temperature environment. (3) Avoid weight-bearing: avoid lifting, pulling or pushing overly heavy objects; avoid heavy physical labor or more strenuous sports activities. (4) Other: restore arm function as soon as possible; wear elastic cuffs when traveling by airplane. (5) Self-care methods for lymphedema: ①Mild or moderate lymphedema: elevate the arm; bottom-up centripetal massage along the lymphatic direction; do arm function restoration training; wear an elastic cuff. ②Severe lymphedema: wear an elastic cuff; physiotherapy. If there are symptoms such as redness or abnormal hardness in the arm, or if the edema is severe, infection should be considered and anti-infection and symptomatic treatment should be given.