Actress Joey King had to put a fellow airline passenger in his place after he confessed he feared he would "catch cancer" from the teen, just because she was sporting a shaved head.

The Conjuring star cut off her hair to play Gypsy Rose Blanchard in new true crime drama series The Act, which centres on a girl who murdered her mother after spending her childhood thinking she had suffered from a number of physical and mental ailments, but was actually in fine health.

The mother and daughter's story hit the headlines in 2016 when journalist Michelle Dean published a Buzzfeed article titled, Dee Dee Wanted Her Daughter To Be Sick, Gypsy Wanted Her Mom To Be Murdered, and now their toxic relationship has been adapted for TV, with Patricia Arquette portraying Dee Dee Blanchard, who battled mental disorder Munchausen syndrome by proxy.

Joey kept her head shaved clean for much of the show's production and quickly discovered just how the style change affected the way people interacted with her when she was out and about - because so many assumed she was undergoing chemotherapy, which often causes cancer patients to lose their hair.

"Some people were like, 'Hey, good luck' and walk away, and I'd be like, 'I'm not sick!'" the 19 year old recalled on U.S. breakfast show Today.

"But then this one guy sat next to me on the airplane and he... took a picture of me... as if I had no idea, and I could see over his shoulder, (he) was texting somebody else he knew on the airplane, like, 'This girl next to me has f-ing cancer. She's coughing, I don't wanna catch it!'"

The crude text message prompted Joey to patronise the traveller, explaining that the disease isn't contagious.

She continued, "I was like, 'Oh man... You know you can't catch cancer? I don't have it, but you can't catch it like that!' It's so ridiculous!"

The Blanchard story features in the first season of anthology series The Act, which debuts on streaming service Hulu next week (20Mar19).

It's not the first time Joey has had a razor-short haircut for work - she went almost bald for her role as a child prisoner in 2012 Batman movie The Dark Knight Rises, while she also shaved her head on camera in Zach Braff movie Wish I Was Here in 2014.