Children’s legs are swollen for no reason, it may be exertion, trauma, allergies, kidney disease or other reasons, you can give rest, cold compresses, anti-infection and other treatments, it is recommended to consult a doctor in a timely manner. 1. Exhaustion: children are in a lively and active stage, excessive activity may occur when the legs are swollen, then generally do not need special treatment, pay attention to rest, observation. 2. Trauma: small children in play hit the leg, may lead to soft tissue damage to the leg and thus suddenly swollen situation. At this time, you can choose a cold compress to reduce swelling, but also need to go to the hospital in time. 3. Allergy: some children may be mosquito bites after the leg allergy, there will also be swelling, this time in the part of the application of anti-allergy drugs, oral loratadine and so on if necessary. 4. Kidney disease: Kidney disease such as nephrotic syndrome can also cause swelling of the legs, you need to go to the hospital to do a comprehensive examination to confirm the diagnosis. 5. Other: local formation of blood clots, poor heart function, tumors, etc. may also cause sudden swelling of the lower legs, but less common in children. Children with swollen legs for no reason may also be related to other reasons, it is recommended to take the child to the hospital to do a detailed examination, a clear diagnosis of the cause, to formulate appropriate treatment programs, and actively cooperate with the treatment.