A medical active substance patch comprising a matrix of monolayer or multilayer configuration with at least one active substance-containing layer and comprising a backing layer connected with the matrix. The active substance patch is transparent or at least translucent, and in the state of having been applied to the skin of a first person, the patch has a lightness colour value L1 at a place of the skin covered by the patch which is not less than 50% and not more than 200% of a lightness colour value L2, L2 being the lightness value of the region of the skin of the same person which surrounds the applied patch. The same is true of the skin of a second or any other person, provided that for all the persons mentioned L2 is in the range from 5° to 100°, namely from 20° to 90°.
