What Is The Treatment For Swollen And Painful Hands?

My daughter has intermittant ( 5-6 times in past 4 months) swelling in her hand in localized spots. Starts out as red mark with apparent bruising then swelling noticable from 10 feet away and painful. Disappears in a few hours or a couple of days. Has happened in the area between thumb and first finger and also the pinky side of her hand.Pediatrician took xrays of hand and did blood work with all coming in normal. Questioning what it is or could be.