The increasingly popular keratin hair treatment, which produces glossy, vibrant and straight hair, originated in Brazil, where it is called escova progressiva, or "progressive blow-dry." The keratin hair treatment is different from chemical straighteners of the past because it does not involve breaking down and restructuring the hair. The older chemical processes permanently change the structure of the hair, but keratin works differently because of its high pH levels, which will soften and not swell the hair and hair cuticle. The New York Times explains the process is executed by applying the keratin formula to the hair; then it is sealed in using a 450-degree flat iron.
Keratin is a type of natural protein that makes up approximately 88 percent of your hair. It is high in the amino acid cystine and is what makes hair “super tough and extremely elastic.” They explain that keratin is a biopolymer, which gives "form and structure to naturally occurring substances,” such as hair and nails, and that the liquid keratin formula “blends with the hair on your head to help restore what has been lost over time.” The New York Times explains that keratin works well because it adheres to the hair and hair cuticle, allowing the hair to contain the moisture, which keeps it hydrated and healthy.
There is a controversy over whether the keratin treatments are safe, since formaldehyde, a known carcinogen, is used in the treatment process. The Los Angeles Times says that it is actually the formaldehyde that straightens the hair. In the Times' report, Dr. Paul McAndrews, a Beverly Hills dermatologist and hair restoration expert, explains, “The keratin fills in the natural defects of the hair shaft, which makes the hair look smoother and silkier, but it does not actually straighten the hair.” The straightening takes place when the 450-degree flat iron seals in the formaldehyde. If you have concerns, Dr. McAndrews recommends discussing them with your hair stylist. In 2014, newer keratin formulations do not contain formaldehyde-related ingredients to chemically straighten hair.
Cylomethicone is another major ingredient in the keratin formula. It is a clear, odorless silicone that is often used as a base solvent in hair, body and cosmetic products. Unlike keratin, it doesn’t really have any healing properties and is considered more as a carrier than a moisturizer. The website 3dchem.com reports that it actually evaporates quickly once applied to the skin or hair, but it is still beneficial in helping the skin or hair feeling “silky smooth” when applied, which is why it is a popular ingredient in the hair and skin industry.