On the basis of general concepts on the objective nature of colour perception and colourimetric tables of the colour atlas special colourimetric rulers were elaborated for the assessment of skin erythema. These rulers can be used for the assessment of experimentally-reproduced common and allergic inflammations of the skin in acute and chronic diseases. The system of assesment take into consideration the experience of the grade characteristics of inflammation of the skin, with the description of erythema with the aid of clear physical colour parameters: brightness (p, %), the wave length (lambda, nm) and the saturation (P,%).