The Sharp Objects star, 21, who was most recently seen in Greta Gerwig’s adaptation of Little Women, plays a teenager with terminal cancer in the Australian movie.
She told the PA news agency: “I was terrified at first, I’m a twin and it was kind of a running joke in my family that I had a big dent in my head from my sister kicking me in the womb, so I had no idea whether that had stayed as I grew older.
“It was relief when we shaved it off and my head was perfectly round, so there was nothing to worry about.
“I realised after shaving it how much I hid behind my hair and it instilled in me a confidence that I didn’t have before and it sounds cheesy but I think it really did transform me.”
She added: “I think that Milla (her character in the movie) encouraged me to be less generic and shaving your hair off is a very good way of doing that to begin with.
“After shaving my head, being out in public felt different at first, it requires a lot of bravery to begin with to step out without any hair and I felt especially uncomfortable knowing that people were going to see me in a certain way and that I was going to receive a lot of undeserved sympathy for an illness that I didn’t have.
“People did assume that i was ill and that was at times quite uncomfortable so it just gave me a lot of perspective really.
She continued: “I think Milla takes risks and through the making of the film, I learned how to take risks as Eliza as well.”
Murphy said it was always important to her to cast an actress who was willing to shave off her hair, adding: “For me vanity in actors is a real turn off because I think the whole point is you shouldn’t be thinking about how you look, you have got to be in the moment of the character.
“It ruled out other people but to be honest, Eliza was someone that we had in mind from the beginning but also I’m really happy to have those strict restrictions on actors and if they then don’t want to even audition because of it, that’s a really easy decision for me.
“I want bold performers who are risk takers so if cutting someone’s hair is an issue then I’m not the right person for you to work with.”
Babyteeth is out now in UK cinemas.
