the problem with hair loss, like everything else in life, is there is not way to package things into nice neat answers.
the itch from male pattern baldness is there for some, not for others. For some its brought on by treatments (especially topicals), for others it goes away with treatments. the truth is there is NO SET RULE: like, if you had itch, and it went away, then you're a golden and propecia will definitely work. the reverse is also true, just because you started using products and your scalp started to itch, that doesn't mean your body is "reacting" to the drugs, so hey it must be working! Thats why its important to take every person's story/treatment/results with a grain of salt. It's THEIR story, and the best way to get informed is to listen to what people say and make your own judgement calls. For example, just because some hairy guy, norwood 2 guy whose 25 sounds just like you says "propecia doesn't work!" doesn't mean it won't work for you. learn all you can from everyone, but don't jump to conclusions
chewy simply asked, why was it that HIS itch went away. a very likely answer is that he is starting to lower his DHT levels, and perhaps that was contributing to some of his itch. For you, it may be that your body is responding to a changing scalp environment, and the response is manifesting itself as an itchy scalp (i.e. less DHT). It all depends. basically, take your propecia, and if an itch comes along, treat the symptoms, and don't read too much into it.
sorry its so long, and i got off on a tangent, but i'm a little bored at the moment.