the enzyme klk5 a serine protease expressed in the epidermis klk5 degrades proteins which form the extracellular component of cell junctions in the stratum corneum and may be involved in the regulation of desquamation the cosmetic compositions for improving the aesthetic appearance of human skin comprise in a cosmetically acceptable vehicle an amount of a salicylic acid dimer effective to improve the aesthetic appearance of skin these salicylic acid dimers may have the structure of formula i where r a and r b are independently selected from hydrogen or c 1 c 12 or c 1 c 10 or c 1 c 8 or c 1 c 6 or c 1 c 4 branched straight chained or cyclic hydrocarbons optionally substituted with 1 4 i e one two three or four heteroatoms selected from halogen oxygen nitrogen and sulfur including without limitation methyl ethyl propyl butyl pentyl and hexyl in some embodiments r a and r b are may independently be selected from hydrogen or lower alkyl e g methyl ethyl propyl butyl pentyl and hexyl in certain implementations r a and r b are both methyl in certain implementations r a and r b are both ethyl in certain implementations r a and r b are both propyl in certain implementations r a and r b are both butyl in each case the lower alkyl may have a subsistent r such as a hydroxyl group or halogen or the lower alkyl may comprise one or more e g from.