What Causes A Sensation Of Swelling In The Limbs?

Doctor, my son keeps telling me that at mornings he feels that his hands and his feet (but more about hands) are swelled and huge, that he feels that every thing, including his other body parts feels like small, and he cannot manage with his "big" hands. It was 3 times recently. He is 11. He got flu recently, we are giving some medicine him from "over the counter" I think maybe it is side effect? I am afraid maybe it is more serious. He was complaining like this one year ago and was gone. Thanks