Sudden swelling of the patient’s hand is commonly caused by hand trauma and allergy, as follows: First, hand trauma: contusions of the soft tissues of the hand, or the occurrence of finger fractures or dislocations can cause sudden swelling of the hand, accompanied by pain and limited movement. The fracture and dislocation can be detected by taking X-ray film, and the pain and swelling can be reduced by continuous cold compress treatment and elevation of the affected limb. Second, allergy: the patient is allergic to cold air or drugs, which can also induce sudden swelling of the hand with itchy skin, and in severe cases, a rash can appear. After identifying the allergen and keeping away from it in time, as well as taking oral anti-allergy medication, such as loratadine, clinical symptoms such as swelling and itching of the hands can be completely relieved. Therefore, the sudden appearance of swelling in the hands should be diagnosed and treated promptly in order to get complete relief of clinical symptoms.