Brazilian hair straightening
Brazilian hair straightening is a semi-permanent hair straightening method done by temporarily sealing a liquid solution consisting of formaldehyde or a formaldehyde derivative and a preservative solution into the hair with a hair iron.
The technique has many variations and is known by several other names and brands, including Brazilian Blowout, Breezilian straightening, Brazilian Keratin Treatment, BKT, and Keratin Cure. It is called Escova Progressiva in Brazil and Alisado brasileiro in Portugal.
The original formulation included formaldehyde H
2CO or methylene glycol H
2C(OH)
2. The two products readily interconvert, and coexist in chemical equilibrium, when dissolved in water or body fluids. Since formaldehyde is a known health hazard, the compositions have been banned in several countries including Canada and the European Union. It is still performed in the United States, though there are regulations and have been controversies regarding the treatment.