The suit takes aim at L'Oreal's no-lye hair relaxer marketed under the Soft Sheen-Carson brand and touted by celebrities like model Cynthia Bailey and Johnny Wright, hairdresser to First Lady Michelle Obama, according to the suit.
The relaxer is responsible for "disturbing and distressing injuries including hair loss and breakage as well as scalp irritation, blisters and burns," said the suit, which was filed Wednesday in a federal court in California.
Plaintiffs already number 100,000, said attorney Ben Meiselas, who has previously represented celebrities, including Michael Jackson.
Meiselas said the penalties could exceed "several" hundred million dollars and told AFP he was "happy" to engage in settlement talks.
"It's up to them if they want to avoid a trial," he said.
L'Oreal defended the product.
"Relaxers are technical products that can be used safely according to the instructions," said a company spokeswoman.
"We cannot comment on this legal action and L'Oreal USA is following the case closely."
In marketing the product, L'Oreal touted its use of amla oil, which is derived from amla, an Indian gooseberry. But the suit argues that the product contained "hardly any" amla oil and was instead filled with a "dangerous mix of irritants and potentially toxic substances."
Plaintiffs include Sharon Manier of California, who was drawn to advertisements that promoted the "rejuvenating" qualities of the relaxer. But Manier immediately experienced scalp irritation, followed by hair loss.
"Plaintiff is currently wearing partial hair pieces to cover up the areas of hair loss and is currently purchasing costly hair vitamins to help her hair regrow," the suit said.
