Swelling of the upper eyelids in young children may be a normal physiological phenomenon, or it may be caused by pathologic reasons, such as nephrotic syndrome, infectious mononucleosis, etc. The swelling of the upper eyelids in young children may be a normal phenomenon. 1. Normal physiological phenomenon: If a child drinks too much water before going to bed or cries excessively, the upper eyelid may appear swollen when the child wakes up early, which is a normal phenomenon and generally does not require special treatment. 2. Pathological causes (1) nephrotic syndrome: patients with nephrotic syndrome have abnormal renal function, patients may show a large amount of proteinuria, high degree of edema and hyperlipidemia and other typical symptoms, and children may also appear to wake up with swollen eyelids. (2) Infectious mononucleosis: Infectious mononucleosis is a self-limiting disease caused by EBV infection, early children may appear to be swollen eyelids, but also with irregular fever, lymph node swelling and other clinical symptoms. It is recommended that children with significant eyelid swelling should be seen promptly for evaluation of their condition and treatment in accordance with medical advice.