Why There's So Little PDA on 'Downton Abbey'

— -- Don't expect a ton of PDA in the upcoming season of "Downton Abbey."

The characters aren't overly touchy-feely with each other for a reason, show historian Alistair Bruce explained.

"I tell the actors not to touch each other. I don't want any hugging, no physical contact. They just didn't do that in those days," he said during an appearance on the BBC Radio 2 show, "The Radio 2 Arts Show with Claudia Winkleman."

"The reason they didn't is wasn't that long before then that disease was spread so much more easily. We hug, kiss – good Lord you meet somebody now and they kiss you within minutes – and it’s because we’ve got antibiotics."

Bruce, an expert on the 1920s who has spent a good deal of time on the "Downton" set, added that as the show increases in popularity, it's even more imperative that every detail of the show is historically accurate.

"It is important getting the detail right and the pressure does increase," he said. "People long to find error!"