The straightening treatment most commonly associated with Japanese hair is also known as thermal reconditioning. During this treatment, hair is treated with a solution that breaks down the keratin in the hair, allowing it to take on any shape. The hair is then flat-ironed in tiny sections, and a neutralizer is used to keep the hair in place. A Japanese hair-straightening treatment lasts up to six months.
Japanese hair straightening takes several hours to perform in the hair salon. After using thermal reconditioning, hair remains straight until the process grows out. The process is permanent; hair cannot be curled or styled while it is in place.
Thermal reconditioning should only be performed by someone who has a lot of experience with the process. Women whose hair has been chemically treated with coloring, highlights or perms should avoid Japanese hair straightening as it can damage their hair badly, causing it to fall out or become "fried."
Many hair stylists prefer the Japanese style of hair-straightening treatment to Brazilian hair straightening, which follows a similar process but uses a significant amount of formaldehyde. Because formaldehyde is a known carcinogen when inhaled, many people have returned to Japanese hair-straightening, which first became popular in the United States in the early 2000s.