Unlike other types of relaxers, the treatment can be used over any kind of straightening.

"The keratin fits right on the hair's cortex," says Nadine Ramos of Brazilian Hair Straightening Inc. in New York's East Village. "It works as a treatment and a straightener at the same time. It actually strengthens the hair's cuticle."

Ramos first heard about the treatment when she got her hair straightened four years ago by a Brazilian importer. She liked it so much, she decided to get licensed so she could provide the service to other women. She has been importing it for three years. But it's popularity has soared this year, she says.

"Stylists see that it works and that it's time efficient," Ramos says.

On average, the process takes around two hours, and starts at around $150. Thermal reconditioning, on the other hand, can take five to six hours and usually costs $500 and up.