What is in the rain that makes us sick?

Philippines
@swirlz (3124)
February 25, 2008 9:23am CST
walking in the rain - shows a couple walking under the rain
There are two types of person when caught in the rain. The one who waits until it would stop and the one who would make a run for it. I'm always the one who would run. lol. My philosophy is "it's just water, it will just dry up". But people keep saying that I would get sick because of this mentality. So I'm asking, what is in the rain that will make us sick? And are you like me, or the type who waits until the rain stops?