Halle Berry and her kids Nahla, 12, and Maceo, six, have been spending a lot of time in their pool while isolating at home amid the coronavirus pandemic.
The daily dips led to her oldest child ending up with "matted fur" at the back of her head due to chlorine damage.
The 53-year-old actress said: "Every day we're swimming, we get out of the pool, My daughter's 12 and so every time I got to comb her hair, she's like, 'No don't touch me, I can handle it, I'm a tween, don't brush my hair.'
"Two nights ago, We're doing her homework and [Nahla] goes, 'Mom, I'm scared to tell you this, but touch the back of my head.'
"All her hair, which is past her shoulders, has shrunken up into a tight ball that feels like matted fur. I can't even get my finger in it, and I'm pulling and she's screaming."
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The actress tried to stay calm and helped Nahla wash her hair and put conditioner in to help work out the tangled locks but it just got "tighter", prompting Halle to shave her daughter's head, leaving her "bald at the back".
Talk show host Jimmy Fallon - who was speaking to the actress via video link - asked if Nahla was "cool" about the move.
She said: "She was not cool with that, but it was our only option. But now she gets it.
"I was like, 'First of all, maybe you'll let your mother help you. And second of all, you learned you gotta brush your hair. Every day, you gotta brush your hair.'"