ABC News' Melissa Lustrin and Juju Chang report:
Keratin was once a high-end treatment used to straighten hair. But now, Suave, the company that brought Keratin to the masses, faces a class action that alleges, among other claims, that one of its products contained formaldehyde and caused significant damage to the hair of some customers.
The lawsuit was first filed last year by women who say Keratin singed their hair and caused it to break off in clumps. The makers of the product tried to get the case dismissed, but a Kentucky federal judge recently ruled that the class action could move forward and it is headed to court.
Tonja Millet of Dallas and Darlene Johnson of Los Angeles are part of the lawsuit against Unilever, the manufacturer of Suave products, claiming Suave Professionals Keratin Infusion 30-Day Smoothing Kit contains harsh chemicals that burned their scalps and even melted or permanently destroyed their hair.
"The product was also advertised as formaldehyde-free, and in fact, we believe that it contained formaldehyde," Millet's attorney, Amy Davis, told ABC News.
Suave did recall the kit in May 2012, but the lawsuit claims the company still didn't do enough to warn customers.
"Many of the women that we represent purchased the product and used the product after the so-called recall," said Davis, who represents 14 women in the suit.
"It has definitely affected my self esteem … my ability to actually want to go places" added Millet.
The lawsuit is also highlighting what many in the beauty industry are calling the root of a growing problem, that many women are turning to chemicals rather than just blow-drying or straightening their hair.
Style expert Gretta Monahan suggests any chemical treatment on hair should be left to the professionals.
"Any time you're permanently changing the hair from its natural state, you're causing damage to do it," Monahan explained. "And that's why it's very difficult to administer those chemicals yourself at home."
Unilever, the company that manufactures the Suave 30-Day Keratin Kit would not comment on an ongoing lawsuit directly but did tell ABC News, "The company takes these claims very seriously," and that "the safety of all of our products is of paramount concern to Unilever."
Hair care professionals ABC News spoke to said that for permed or color-treated hair, great care must be taken in adding more harsh chemicals, even if the product says it's formaldehyde-free. The Suave 30-Day Smoothing Kit did come with several warnings for the types of hair that might not react well to the product, but at least one of the women we spoke with who is a plaintiff in the lawsuit said she didn't fall under any of those categories and still had terrible results.