People with Raynaud’s disease are at the other end of the spectrum from people who blush at the drop of a hat. But, instead of having blood vessels that open readily, they have vessels that constrict too easily, usually in response to something cold. When you have Raynaud’s, you can walk into an air-conditioned room or even reach into a picnic cooler, and suddenly your fingers feel oddly cold, even numb and tingly. As you watch, the tips go dead white, then blue, and (after you frantically warm them up again), a bright, throbbing red.