Why does my gas smell so very nasty?

So every now and then, since I have high cholesterol I require myself to eat Honey Nut CHeerios. Well....I have horrid nasty gas all day long and its the silent but deadly type. Now, I know its these cheerios. Is it something in them, OR is it a reaction my body saying it doesn;t like these things? Whats going on ? I have read some info online, and a lot of people say its due to Lactose INtolerance, but I have no problem with dairy products, except the throat issues.