Adult performers are general term. What do you mean? There are lots of job related to this.
Be allowed? Haha funny. Who will allow them to? Silly and
ridiculous question

You have problem about asking questions?
The thread which exist below already has full of posts, arguments, stories and opinons.
If someone wants to read:
http://board.freeones.com/showthread.php?665990-pornstar-has-a-***