This test method relates to the evaluation of the ability of a skin care product to reduce the visible appearance of stretchmarks and scars.

The measurement of stretchmarks and scars are based on a visible evaluation of precision photography to determine the effect of the test product on the test site. A trained laboratory technician would perform the evaluation and utilise a rating scale. Further, it may be requested that the volunteer provide feedback as to the visible changes from the scar or stretch marks.

Further, the measuring principle of the instrument utilised for this type of instrumental substantiation is based upon the suction method, where negative pressure deforms the skin mechanically. Pressure is created inside the device and draws the skin into the aperture of the probe and after a defined time, releases it again. Inside the probe, the penetration depth is determined by a non-contact optical measuring system. This optical measuring system consists of a light source and a light receptor, as well as two prisms facing each other, which project the light from transmitter to receptor. The light intensity varies due to the penetration depth of the skin. The resistance of the skin to the negative pressure (firmness) and its ability to return to its original position (elasticity) are displayed as curves (penetration depth in mm/time) in real time during the measurement. From these curves a variety of specific measurement parameters can be calculated in relation to elastic and visco-elastic properties of the skin surface and skin aging.