Jon Hamm. (Reuters file photo)

The stress of shooting Mad Men has landed the period drama's star Jon Hamm with a nasty case of vitiligo.

The actor's hands have become discoloured in places thanks to the skin disease and he puts it down to the long hours he spends fretting about his character Don Draper on the show.

He tells Rolling Stone magazine, "You do have to be mentally acute for a significant period of time, and that becomes pretty draining.

"I have vitiligo. It's stress-oriented. It comes and goes and waxes and wanes. This did not exist before the show."