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 L<；SUB>；1 <；/SUB>；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 L<；SUB>；2<；/SUB>；, L<；SUB>；2 <；/SUB>；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 L<；SUB>；2 <；/SUB>；is in the range from 5° to 100°, namely from 20° to 90°.
