Universe | Science | Facts on Instagram: "Raynaud’s phenomenon causes blood vessels in the fingers to narrow in response to cold or stress, leading to pale or bluish skin, numbness, and pain. When the affected finger is placed in warm or hot water, the blood vessels begin to dilate (open up). This improves blood flow, bringing back normal color, warmth, and sensation. The tingling or mild pain felt during warming is a sign that circulation is returning. Controlled warmth is one of the simplest w