Sudden swelling of a child’s hand may be caused by contusion, angioneurotic edema and other factors. 1. contusion: if a child accidentally falls, it will make the hand contusion, which will make the local inflammatory exudation, causing sudden swelling of the hand. 2. Angioneurotic edema: For example, if a child’s hand is bitten by a mosquito, the mosquito will inject saliva into the local skin, thereby stimulating the immune system, resulting in increased local vascular permeability, causing sudden swelling of the hand. Children’s hands suddenly swollen, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.