A mother pours cleaning chemicals into her sons soup and he gets really sick. The daughter starts to notice something weird going on. The mother also sprays something on the little boys back and rubs it in with a sponge, which causes him to get a rash. What's this movie called?

Possibly this? (the second link is a discussion on why the mother rubbed the boy with oven cleaner... )
Glass House: The Good Mother (Video 2006) - IMDb (http://www.imdb.com/title/tt0498348/)

Oven Cleaner - IMDb (http://www.imdb.com/title/tt0498348/board/nest/74816833?ref_=tt_bd_5)