Same thing happened to my ds over summer just gone. He had clarantyne, only two doses and swelling went down.
Not sure how old your child is but mine is 3 and the dr also got me to worm him. The worms take a lot of vitamin b from their little bodies which causes the reactions. Also we now Give him pentavite vitamin just to keep him boosted up!
We did the one time conbantrum wormer!