There are many reasons why children’s ankles are swollen for no reason, such as foot sprains, kidney disease, mosquito bites and so on. 1. Foot sprain: when children are walking, if they accidentally fall on a heel, it is very easy to cause red and swollen ankles. 2. Kidney disease: when the child suffers from nephritis or other kidney diseases, it will cause abnormal kidney function, and the water in the body can not be discharged out of the body through the kidneys in time, which may lead to swollen ankles in children. 3. Mosquito bites: because the skin of small children will be more delicate, once the mosquito bites, it is likely to appear ankle swelling. Children’s ankles swollen for no reason, there may be other reasons, need to go to the hospital in a timely manner for medical treatment, to find the specific reasons for targeted treatment.