If you think you have mold, don't reach for chlorine bleach. Yes, bleach will kill virtually every kind of mold it comes in contact with, but it only works on nonporous materials like ceramic tile and glass. It does not penetrate materials like drywall and wood, where most people have real mold issues. An alternative is to use nontoxic borax to kill mold. Borax has commonly been used as a natural insecticide, so it's highly effective at remedying other problems, like toxic mold.