This isn't my joke. A friend told it to me but I think that he heard it from someone as well.
A man meets a woman at a seedy dive bar. Eventually last call comes and they leave together. They go back to her place and walk to her bedroom. She tells him to sit on the bed while she "gets more comfortable". She comes back and turns off the bedroom light as they begin to fool around. Eventually, deep kisses turn to more intense action. Finally, they are "doing it". He stops her and tells her that something doesn't feel right. He takes off his shirt thinking maybe something was getting in the way. They start back at it. Moments later he stops again. "Here let's try some lube" the woman tells him as she reaches into her night stand. They start back at it once more. Once again, he has to stop because something isn't feeling right. Without another thought she says, "wait right here", and leaves to her restroom. She comes back and IT...WAS...ON. He slides in no problem and is audibly impressed with how good it feels. Afterwards, as they laid in bed he asked, "Oh my God, that was amazing. What did you do?". "I peeled off my scabs," she said.