Keratin Hair Treatments: Your Ultimate Guide

Freedom from frizz, once and for all.

model with sleek shiny hair
(Image credit: Getty)

If you've ever experienced even a tiny bit of frizz, you've probably been told by a friend or hairstylist to try a keratin treatment (other names include "Brazilian blowout" and "smoothing treatment"). A keratin treatment has been deemed the "miracle" way to get smoother, shinier hair in just one appointment at your local salon—or you can make use of an at-home keratin treatment, if you prefer. 

But like most chemical-laden beauty treatments, not all keratin treatments are created equal, nor are they for every hair type. And navigating the misinformation on the interweb can be overwhelming. To clear the air before you make the plunge towards sleek glory, I went to the experts to find out what you need to know about keratin treatments.

What Is a Keratin Treatment?

"People use different names for different treatments interchangeably, which is just incorrect," says Meri Kate O'Connor, hairstylist and colorist at Tabb and Sparks salon in Los Angeles. "You either have your traditional keratin treatment, commonly called a Brazilian blowout, which really straightens out your hair texture,” she says, “or you have your smoothing treatments, like Goldwell Kerasilk, which help de-frizz hair and add shine, without disrupting its texture.”

In short: If you’re happy with your waves and curls but would love to cut down on frizz (and loosen your texture), get a smoothing treatment. If you want your hair to look flat-ironed straight, go for the Brazilian blowout, a.k.a. a keratin treatment.

Keratin Treatments vs. Smoothing Treatments

Most hair-smoothing treatments involve the use of the protein keratin—which explains why people lump them all under "keratin treatments"—but keratin isn't really the shining star of the treatments—the other ingredients are.

"A traditional keratin treatment aims to straighten the hair and usually involves a formaldehyde-releasing solution," says O'Connor, noting that your stylist will saturate your hair with the solution for 20 minutes—"it basically coats your hair cuticle like armor"—before it gets blow-dried and methodically flat-ironed. "The entire process, when done correctly, will straighten out your hair texture and completely eliminate frizz for up to three months," she adds.

"Smoothing treatments, on the other hand, are formaldehyde-free and deeply permeate the cortex of your hair, rather than sit on the outside of your cuticle, to smooth your hair," she explains. While the application process is similar, the formula isn't as potent (formaldehyde is necessary for that flat-ironed look), but don't expect it to straighten your hair. "It will, however, last longer—generally anywhere from four to six months," says O'Connor.

Are Keratin Treatments Safe?

Unfortunately, safe-enough-to-eat hair-straightening systems at the salon simply don't exist. If you want to take your texture from coarse and curly to flat-iron straight with a salon keratin treatment, you'll need some formaldehyde—which has a pretty bad rap.

"According to the EPA, formaldehyde is a carcinogen that could possibly cause respiratory problems if exposure is frequent," says Brenda Kamt, colorist specialist at 454 North Salon in Los Angeles.

Even if your salon uses a formaldehyde-free straightening treatment, the chemical may still be present. "Formaldehyde isn't actually a single ingredient—it's a gas that's emitted from other chemicals being exposed to heat," explains Kamt. "So technically, a product can say it's formaldehyde-free, but still contain the ingredients that create the gas."

That said: "If you're only getting the treatment done three times per year...the risk is very minimal,” Kamt says. “Make sure you're having the process done in a well-ventilated salon, or, even more ideally, with windows open or outdoors.”

After Your Keratin Treatment

"If you get a traditional keratin smoothing treatment, you can't really touch your hair for three days afterward," says O'Connor. "You can't clip it back, you can't put it in a ponytail, and you can't wash it, or you'll risk denting it."

If your hair is colored, you also run the risk of minimal fading or lightening after the treatment, though both experts say it isn't that common.

"Although it depends entirely on the keratin line you're using, you might experience some very slight lightening—like, less than a shade—of glosses, toners, or any demi- or semi-permanent colors," says Kamt. "This is mainly due to the use a clarifying shampoo prior to the keratin process, which is used to remove residue from hair, but may also remove some color."

In the weeks and months after a treatment, make sure to give your hair a little TLC with a hair mask, like our picks below, that will nourish and protect your newly smoothed hair.

What Will a Keratin Treatment Look Like?

"In theory, a traditional keratin treatment should straighten even pretty tight curls, but I've seen women end up with slight waves that they still need to flat-iron," says O'Connor. "I've known women whose curls were totally unaffected by smoothing treatments, while others saw their curls loosen to waves."

It all depends, says Kamt, on the strength of the treatment is, how it's applied, the temperature of the flat-iron, how porous your hair is, and about other factors you really can't control. But don't let that scare you away. "Just do your research, read a ton of reviews, and talk openly with your stylist about what you do and don't want," says O'Connor. “After all, it'll wash out in a few months, anyway."

Meri Kate O'Connor
Meri Kate O'Connor

Meri Kate O'Connor is a hair stylist and colorist at Tabb and Sparks salon in Los Angeles.

Brenda Kamt
Brenda Kamt

Brenda is a multi-faceted hair colorist working out of 454 North Salon. She specializes in natural beachy blondes and dimension rich brunettes.

Chloe Metzger
Beauty Editor

Chloe Metzger is the deputy beauty director at Cosmopolitan, overseeing the editorial content and growth strategy of the hair, makeup, and skin space on digital, while also obsessively writing about the best hair products for every hair type (curly girl here; whattup), and the skincare routines that really, truly work (follow her on Instagram to see behind-the-scenes pics of that magazine life). She brings nearly a decade of writing and editing expertise, and her work has appeared in AllureHealthFitnessMarie ClaireStyleCaster, and Parents. She also has an unhealthy adoration for Tom Hanks and would like to please meet him one day, if you could arrange that. Thanks.