Salicylic acid (also called beta hydroxy acid or 2-hydroxybenzoic acid) in a low pH solution applied directly to the skin and left there until next washing. Use daily. Takes weeks to make a big difference and must be continued indefinitely, as it is not a one-time cure, but an ongoing treatment. Read about it at
Paula Begoun - The Cosmetics Cop - Paula's Choice (I have no financial interst in this commerical website) and at
Salicylic acid - Wikipedia, the free encyclopedia.