Bentusa employs reverse pressure when we apply it to the skin. It creates vacum pressure that lifts the skin like in doing pisil manipulation.
In hilot masahe, pisil make space so that healthy blood can circulate well but the poor unhealthy blood will be caught up by the reverse pressure thus making mark on the skin.
This marks shows the unhealthy blood into the skin by dark red, violet to black mark. These marks are the poisnous blood that could be expelled out by applying hagod pressure.