Journal of Cosmetic Dermatology, 12, 144--148 Brazilian keratin hair treatment: a review Courtney Weathersby, MS, 1 & Amy McMichael, MD 2 1 University of Virginia School of Medicine, Charlottesville, Virginia, USA 2 Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA Summary Brazilian keratin treatments are widely available products that are used by women all over the world to straighten hair. Marketers of these products claim that the keratin treatments render naturally curly hair more manageable and frizz-free while enhancing color and shine, giving the hair a healthier appearance. Although widely used, there have been virtually no reports of adverse side effects. Unfortunately, many of the products that are applied by salon professionals contain formaldehyde or its derivatives and are being marketed as safe. Keywords: African hair, Afro-ethnic hair, straightening Introduction For most women, hair is an important feature that contributes to one’s individual identity and can be used as a vehicle to express beauty, attractiveness, and indi- viduality. 1,2 Having more manageable hair that defies humidity has been a long-time desire among women from various ethnic groups. This is evident in the mul- titude of straightening and smoothening techniques that are used across the globe. Historically, flattening irons and pressing combs that add heat to modify the hydrogen bonds of the hair, as well as chemical straighteners, which restructure the disulfide bonds of hair, have been used to cause straightening of the hair. Unfortunately, these mechanisms can weaken the hair shaft causing increased hair fragility, damage, and breakage. 3 Early studies that have looked at hair fragil- ity in Black or African hair in comparison with Cauca- sian and Asian hair have concluded that the biochemical components of the hair among these groups are identical and that hair fragility seen in Afri- can hair was due to structural shaft damage. 4 More recent studies have shown that the outer root sheath and the connective tissue sheath are not symmetrical along the follicle and are thicker on concave side. 5 These studies also showed that the proliferative matrix is different in curly hair. This suggests that heat and chemical straightening methods may work differently depending on hair type. With the advancement of hair care chemistry and tools, hair straightening techniques are becoming more sophisticated, allowing for easier and more durable straightening of the hair. The Brazilian keratin hair treatments are a newer hair straightening method that has recently gained popularity due to its ability to straightening the hair with additional claims of decreasing frizz and increasing shine for up to 5 months. The aim of this article is to review the cur- rent data on keratin-smoothening treatments, the sci- ence behind the treatment, and the issues surrounding the treatment. Brazilian hair straightening: what is it? Brazilian keratin hair straightening, also known as ker- atin smoothening or keratin straightening, has grown in popularity as the treatment of choice for those who wish to maintain straight or relaxed hair for long peri- ods of time. Brazilian hair straightening originated in Correspondence: A McMichael, Department of Dermatology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1071, USA. E-mail: amcmicha@wfubmc.edu Accepted for publication December 22, 2012 144 © 2013 Wiley Periodicals, Inc. Review Article