Swollen baby legs with hard lumps may be caused by trauma, mosquito bites, eczema and other reasons. 1. Trauma. Due to the legs accidentally collision, wrestling and other reasons, resulting in trauma to the legs, thus appearing the phenomenon of swollen legs with hard lumps. 2. Mosquito bites. Hot weather, easy to be mosquito bites, if the bite site is infected by bacteria, the skin may appear red, swollen and hard phenomenon. 3. Eczema. Due to chronic infections and other reasons, eczema is caused, which leads to the phenomenon of redness, swelling and hardness of the child’s legs. Baby legs swollen with hard lumps, 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.