When it’s warm or you’re working out, your body has to find ways to release excess heat, cooling the blood—and you. The capillaries in your face are very near the surface of your skin, so when you’re overheated, blood vessels in your face dilate (open wider), allowing more red blood cells to flow through them and release heat outside the body. When you blush for emotional reasons, the same thing is happening to your blood vessels, but there isn’t a physiological function (that we know of!).

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