Disturbed blood flow from the capillaries causes red discolouration in the face. This can range from a light pink glow to a fierce red network of visible blood vessels. With infrared laser light or green intense pulsed light (IPL) the damaged capillaries are destroyed while the skin surface is protected by a cooling system. This can cause skin irritation for a few days afterwards but mostly the side-effects are very limited.
The first and the last images of the following animations are "before" and "after" pictures. The transition has been rendered digitally.