Mum-of-one January (35) has told how she has been losing her hair in clumps following years of dyeing it for her role as Betty Draper.
But Dublin hairdresser Dylan Bradshaw says Irish women who are fond of dyeing or highlighting should be able to avoid the same fate.
"January over-bleached her hair," Dylan explains.
"On Mad Men she had to dye it every week. There can be no roots showing on TV -- it ruins the continuity."
Dylan says January simply went one dye job too far. "Putting that much bleach on your hair is never a good idea," he says.
"It's a chemical. If you're constantly dying it then you're going to kill the hair. Then it becomes brittle and breaks off -- and that's why you get bald patches."
Dylan says the best advice he can give women is to care for your hair.
"If you dye your hair, make sure to get good hair-care products. If hair is overly processed it could start to break. Use a good conditioner and your hair will stay in good shape."
Women who use highlights or lowlights when colouring their hair won't encounter the same problems. For women highlighting the hair, the recommended minimum period between hairdresser appointments is six weeks.
However, if women are using bleach or dyeing their hair as often as once a week, it will lead to bald patches.
"I would recommend applying lowlights to the root and highlights to the root to avoid this happening.
"She had applied bleach on a weekly basis to pre-lightened hair. The overlap of the bleach was weakening the hair follicle and caused it to break at the root which creates bald patches.
"You have to allow time for regrowth. And condition your hair," he said.
But X Men: Origins star January could have done with this advice a long time ago.
She has previously dyed her blonde dresses brunette and red for various roles.
Now she's claiming her bald patches are so bad from dyeing her hair, she is planning to shave it.
"I have been every colour and now my hair is falling out in clumps," she said.
"I'm going to have to shave it off and wear a wig."