It is very normal to have a darkening of some areas of the skin after an IPL treatment. You can think of the light generated by an IPL device as a huge controlled light bulb. When it flashes, the darker areas of the skin, freckles, sun damage and any other dark areas will absorb most of the energy. This is similar to a black sweater absorbing the heat from the sun on a bright and sunny day. When the pigment (freckles, sun spots, etc.) in the skin absorbs this light energy from the IPL it can destroy the cells that contain the pigment. These dead skin cells come to the surface of the skin in a period of days or weeks after the treatment and appear much darker than the surrounding skin. As part of the normal process, these darker areas will flake off and be replaced by skin tissue without the pigment. This in fact is how the IPL works to get rid of freckles and sun damage so what you are experiencing sounds perfectly normal.