Deodorant Etiquette

I think I forgot to put BO-derant under one pit... not both, just one. I am thinking this because I reached to grab something and got a WHIFF--now, my question is this: Do I have to wash the pit before applying deodorant or do I just apply on stinky pit? I never know what to do in these situations, and Miss Manners has not answered any of my letters since the "does swimming in a chlorinated pool count as a bath for children" question. Usually I would wash, but I am not going anywhere or doing anything today so really... what is the point? Oh the things that dominate my brain...