The good news. According to the best medical authorities, a cotton undershirt will indeed keep you cooler while serving as a barrier between any perspiration and your dress shirt.

How does it do it? A thin cotton layer will actually wick the sweat from your skin, which helps regulate body temperature. Plus, the fibers do create very small pockets of air—just enough to cool the skin slightly.

But buy the right one. You don't want a thick, bulky undershirt. Nor do you want a crew neck peeking out from your oxford. We've tried countless brands over the years and our money's on Hanes' Tagless V-necks. Thin yet durable, they easily tuck under dress shirts but could stand on their own as well.