Renée Zellweger was 'allergic' to The Thing About Pam prosthetics

Renée Zellweger was "allergic" to the prosthetics she wore in The Thing About Pam.

During an appearance on The Tonight Show Starring Jimmy Fallon on Monday night, the Oscar-winning actress discussed how it took make-up artists up to four hours to transform her into Pam Hupp for the crime drama series, which details Hupp's involvement in the 2011 murder of Betsy Faria.

As part of the chat, Zellweger admitted acting in the prosthetics was very uncomfortable.

"I was so allergic to the adhesive it was hilarious, y'all. Lots of Benadryl. Lots of Benadryl," she shared, referring to the antihistamine medication. "Well, I didn't know that it's a whole different skill that I didn't know I didn't have. And I really didn't have it. I really didn't. By the time you get it on, you're so excited, and then you stand there and you go, "Oh, wait, I think I'm allergic to this?'"

Zellweger went on to credit make-up artist Arjen Tuiten for his commitment to the look.

"He's a genius. He does the cast, and then, he hand paints everyone down to the freckles," the 52-year-old explained, noting that all of the time in the make-up chair allowed her to catch up on errands. "It's great. You know, you can call your mom in the chair, you get your emails done, Christmas shopping..."

The Thing About Pam is scheduled to premiere on NBC on Tuesday.