After a shower, you need to add deodorant and anti-antiperspirant to your underarms. There are strong antiperspirants on the market that will help with sweating if you sweat a lot, they can be bought in most pharmacies and grocery stores for a couple of bucks. I'll apply my antiperspirant liberally if I'm going to be somewhere warm or somewhere my arms are going to be motion restricted like on a plane. It's courtesy to others, plus I don't like the smell of B.O.