This has obviously gotten many good replies so I'll keep mine brief. DON'T WORRY ABOUT IT. A little moisture won't hurt anything. I carry IWB and I sweat a good bit. Human perspiration is much worse for a gun than rain. Just give it a decent cleaning/drying and treat with the usual lube when you get back home and you will be golden.
Edit: Oh, and about your ammo. Modern cartridges have a very tight primer pocket so you have a very snug primer fit. Moisture will not be a problem, unless, for example, you drop a full mag in your toilet and don't notice it for a few days. I have heard of people putting nail polish on their primers, but it's best not to mess with it. Nail polish will harden and make it potentially more difficult for the firing pin/striker to get a good enough hit to ignite the priming compound. If you still feel the need to do it, then just a very thin line around the perimeter of the pocket/ primer junction is all you need. But again, I would advise against it.