M.C.
Don't know the ingredient but try having the child drink prune juice. A little everyday works wonders! My daughter used to drink about 2 oz every morning with breakfast. She never minded the taste either, she kind of liked it actually.
The other suggestion I heard from my pediatrician was to alternate pineapple juice and apple juice daily. My daughter pretty much eats pineapples every day so this has worked well also.