Good points there from FB & JK - even tech tops will rub you when they get wet, and then you get "pert" from the cold wind - ouch!
If you're in a race and start getting sore then look out for the St Johns ambulance who will have vaseline to hand, you will usually pass several teams of these on the bigger/longer events, just smear a blob on each side & bobs your uncle - (this works - Ahem - "downstairs" too!)
Incidentally, not many people realise that you can carry a good "blob" of vaseline quite easily in a folded over piece of clingfilm that will fit in the "key" pocket of your running shorts....Just thought I'd mention it...