This question was already answered wasent it?
If you go back far enough, and look at what Serial_Tickler said, he mentioned when did the nails of and tickled Jessica Simpson (who was mighty ticklish), she asked if he would do her too. And she was. Here's what he said, quoted from the post-
Jessica Simpson: Jessica has ticklish feet as well, she seemed to be ticklish on her soles and and heels, I used the pumice and brush on her soles and she kept laughing, i would stop but she told me it was ok and to not mind her. so when i continued she kept laughing more. Also she asked me if i would mind giving her sister (I think she is one of her dancers) one i did and she was also ticklish but did'nt take it as long, I only was able to use the pumice stone on her.