Have you located the water source? If not that should be your first step. Completely dry that area and make sure it can't get wet again and that will keep it from continuing to grow. You can use products like bleach to kill the mold and wipe away the topical areas, but the dead spores that will still be there can still cause a reaction. So if your pretty allergic to the stuff, you may want to dry it, clean it, then seal it off until you can replace it.