Why do we look red when were hot?

The skin's appearance changes when a person becomes hot because of increased blood flow to the skin's surface. This increased blood flow causes the skin's blood vessels to dilate, allowing more blood to pass through them. The increased blood flow brings heat to the skin's surface, causing the skin to feel warm to the touch. Additionally, the increased blood flow causes the skin's capillaries to become more visible, giving the skin a red or flushed appearance.