The light, which isn’t reflected off the skin’s surface (a). scatters beneath the skin’s surface, (b) is then absorbed in the melanin and blood. The melanin is coagulated by the absorbed heat energy and in blood vessels the heat absorbed by the blood is conducted to the delicate vessel walls (vascular endothelium), whose cells are damaged by the heat causing the vessel to collapse or completely coagulate.
Illustration: Example standardised spectral distribution of a typical xenon lamp IPL (iPulse. Cyden Ltd) measured in 20 nm bandwidths as a percentage of the total energy beneath the graph curve. Absorption curves for oxyhaemoglobin (red) melanin (black) and water (blue) have been overlaid to reference optimal absorption characteristics.