Ditto cornflake. A phobia can grow out of a rational fear, but expresses itself in far less rational ways. For example, I'm afraid of heights and confined spaces and sharks. But those are all rational fears, and they don't stop me from doing things I really want to do (like flying in airplanes or swimming in the ocean), so I don't consider them phobias.

I have two phobias, one of which (dead bodies) is based on a rational fear. This one does interfere with my life: When my cat kills mice, I shut myself in my bedroom and am too scared to come out until someone else not me has disposed of the corpse. If no one else is home and I can't just hide in there all day, it's like I'm in a horror movie: inching along, eyes wide open, almost in tears, jumping at every tiny sound, looking around wildly for the horrible thing I know is here somewhere.

My other phobia (fear of balloons) is based on an irrational fear. I am fine with Mylar balloons, and a little uneasy but basically fine when rubber balloons are being used as decoration and no one is touching them. But anyone touching a balloon scares me so much I can't stay near it; I feel like something is literally pushing me away from it, the instinct to run is so strong. I have noped right out of little kids' birthday parties many times.