Hollywood actor Dustin Hoffman has a secret behind his youthful looks - he still suffers from acne. The 70-year-old still takes medication for the skin condition and insists that the drugs have helped slow down the ageing process. He says, "It's a double-edged sword. I had maybe the world's worst case of acne. I could go into the Guinness Book of Records for having the oldest case of acne - and I still take medication for it. "I don't mind it as much as I used to, but having said that, it gives me oily skin which tends to give me less wrinkles which tends to allow my hair to stay on my head, so it's my revenge."