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DOI: 10.1111/jdv.13028

REVIEW ARTICLE

Clinical and anthropological perspectives on chemical relaxing of afro-textured hair S.A. Aryiku,1 A. Salam,2 O.E. Dadzie,3 N.G. Jablonski4,* 1

Nottingham University Hospitals NHS Trust Nottingham, Queen’s Medical Centre, Nottingham, UK Imperial College Healthcare NHS Trust, London, UK 3 Departments of Dermatology and Histopathology, The North West London Hospitals NHS Trust, Northwick Park Hospital, Harrow, UK 4 The Pennsylvania State University, University Park, PA, USA *Correspondence: N.G. Jablonski. E-mail: [email protected] 2

Abstract The culturally engrained practice of ‘relaxing’ afro-textured hair has been linked with hair and scalp disorders. Herein, we discuss the evolution of human hair types, focusing in particular on afro-textured hair. We explore the biological features of this hair type, and discuss the different methods employed to straighten afro-textured hair, focusing in particular on chemical straightening. We also examine clinical, anthropological, and psychological issues associated with this latter practice. Examples of common scalp pathologies associated with chronic hair relaxing, such as alopecia, hair breakage, caustic burns and irritant contact dermatitis, are also highlighted. The data presented herein should enable clinicians to engage in culturally appropriate discussions with their patients about issues of appearance and conformity. Received: 2 October 2014; Accepted: 13 January 2015

Conflicts of Interest al. She served as a speaker for Beiersdorf Dr Ophelia E. Dadzie has received research sponsorship funding from L’Ore and Stiefel, a GSK company for which she received honoraria and she is the founder and director of London Ethnic Skin al and served as a speaker for LVMH Limited; Professor Nina G. Jablonski serves on the scientific advisory board of L’Ore for which she received honoraria.

Funding sources None.

Introduction Chemical relaxation of afro-textured hair is a culturally engrained practice implicated in the aetio-pathogenesis of a range of hair and scalp disorders. In this article, we explore the evolution of human scalp hair, focusing on afro-textured hair, as well as the distinct biological features of this hair type. Current evidence pertaining to hair straightening, in particular the use of chemical relaxers and their associated adverse effects are discussed. Pertinent sociological, anthropological and psychological issues associated with chronic hair relaxing are also highlighted. The data presented herein should enable clinicians to engage in culturally appropriate discussions on issues of appearance and conformity with their patients.

and does not take into account the variability seen within and between groups. For this reason, Loussouarn et al.1 developed a new classification system, (based on the work of Hrdy2 in relation to morphological parameters for characterizing scalp hair) using objective criteria (i.e. curve diameter, curl index, highest number of waves and number of twists) to classify human hair types into eight distinct groups, independent of ethnicity and race (Fig. 1). This classification system shows clearly the diversity of human hair types. Understanding how human hair diversity has evolved is important for understanding current hair grooming practices, yet this area remains relatively unexplored in the scientific literature.

Evolution of human scalp hair phenotypes Human hair diversity and classification Human scalp hair has traditionally been classified into three major groups: Asian, Caucasian and African based on macroscopic characteristics. This taxonomy is archaic and misleading,

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The evolution of human scalp hair phenotypes has not been adequately studied. This is remarkable considering the importance of hair in human culture and in self-perception. Scalp hair has been studied from many aspects: the aetiology, significance, and

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Figure 1 Classification of human scalp hair phenotype. (Reprinted with permission from Wiley-Blackwell).1

mitigation of different types of hair loss has preoccupied dermatologists, whereas care and management of different hair types and colours have dominated the work of cosmetic scientists and aestheticians. Anthropological studies of scalp hair are few. The morphological characteristics of human scalp hair were noted in the characterization of human varieties and races in the 17th and 18th centuries, but these descriptions were cursory and superficial. Typological classifications of hair form were developed in the 19th and early 20th centuries, but the first systematic description and comparison of hair structure was undertaken by Hrdy in the 1970s. Hrdy described eight morphological parameters by which scalp hair could be accurately characterized: diameter, medullation, scale count, kinking, average curvature, ratio of curvature, crimp, and ratio of natural to straight length.2,3 The most variable parameter between populations was average curvature, followed by regularity of curling and crimp; other morphological features including diameter, medullation

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and scale count were far less important in differentiating populations. Hrdy opined that hair form was determined by multiple genes, and that tightly curly hair form had evolved convergently in African and Melanesian populations because of similar environmental pressures, but did not speculate on the possible functional significance of hair form. Since Hrdy’s research, comparative studies of hair form have focused on forensic applications,4 not on phylogeny and function. The latter questions are being approached slowly, as variant genes associated with distinct hair phenotypes are identified. Identification of genes responsible for variations in hair pigmentation has preceded that of genes for hair form.5,6 To date, only the variant EDAR 370A gene has been unequivocally associated with human scalp hair form, specifically with the thick straight hair shafts common in East Asians. This variant was identified in a genome-wide scan for natural selection in the human genome, and is associated with a high density of eccrine sweat glands. The

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EDAR 370A variant was brought to fixation through a selective sweep, but the question of what was being selected for eccrine sweating, thick hair or both has not been resolved.7 Hair form is almost certainly related to thermoregulation and the importance of keeping the head cool during exercise and under hot environmental conditions,8,9 but comparative studies of the effects of different hair forms on scalp and body temperature have not been conducted. No genetic or functional evidence yet supports Hrdy’s logical surmise about convergent evolution of tightly curled hair forms.

Biology of afro-textured hair The chemical properties of all human hair types are very similar, however, the unique tightly coiled afro-textured hair displays distinct biological and structural differences.10 The hair shaft of afro-textured hair has an elliptical cross-sectional appearance, with marked variation in shape and diameter, as opposed to the oval and circular cross-sectional appearance of hair found in Eurasian peoples.10,11 There is also retro-curvature of the hair bulb of this hair type, creating an asymmetrical S-shaped hair follicle.12 Studies indicate that the curly shape of this hair shaft is intrinsically programmed by the follicular bulb.5,13 Hair with a lower curl diameter and therefore a higher visual curl degree has been shown to have a lower Young’s modulus (a measure of elasticity), break strain and break stress and is consequently more susceptible to breakage.14 Syed et al.15 showed that break stress and break elongation of untreated African-American hair is lower than that of Eurasian peoples and that this tensile strength is even lower in wet hair states, and hence more fragile under these conditions. Also highly characteristic of afro-textured hair, is the presence of both complex and single strand knots, thus leading to an increase in resistance during combing.16 Syed et al.15 have also demonstrated that African-American hair has lower moisture content when compared with Eurasian hair, thus making this hair type more susceptible to breakage, especially during grooming. Afro-textured hair grows at a slower rate than European and Asian hair (mean  SD: 280  50, 367  56 and 411  43 lm/ day, respectively) and is found more frequently in the telogen phase, especially in the occipital and temporal regions.17,18 Slower hair growth rate in conjunction with an increased susceptibility to breakage may explain the shorter hair lengths achieved by those with afro-textured hair in comparison to Eurasians.

Overview of hair straightening Ancient Egyptian women were the first to practice hair straightening using heated flat iron plates.19 Over time this technique was modified, leading to the development of the ‘hot comb’, first used by French women during the 19th century.19 The latter is a metal comb that is heated on a burner or stove up to 300–500°F and then pulled through curly hair. By temporarily breaking and

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re-arranging weak hydrogen bonds between keratin filaments, a new straight texture is achieved and is maintained until contact with water. For all of known human history, African men and women have ‘groomed’ their hair, and many old painted, sculpted and carved images from 4000 BC onward attest to this. As a practice, hair grooming no doubt long predates this time. There is no evidence of widespread hair straightening, however, until after the practice was introduced from the U.S. in the latest 19th and early 20th centuries. In the early 1900s, Sarah Breedlove, later known as Madame C.J. Walker, created a pomade using a combination of oils, to treat her own hair loss.20 Marketed as Madame Walker’s wonderful hair grower, this was the first of five original products later known as the ‘Walker System’.19 Contrary to popular belief, these products were not initially developed to straighten hair, but to cleanse the scalp and hair, heal scalp disease and prevent hair loss. However, when used in combination with the hot comb, a temporary straightening effect was observed, and this led to the development of the ‘Shampoo-press-and-curl-Walker System’.19 Chemical hair straighteners were subsequently developed to meet the demand for permanent hair straightening. These ‘chemical relaxers’ revolutionized and continue to dominate the black hair care industry. Recently a semi-permanent treatment (‘Brazilian Keratin Treatment’ or ‘Brazilian blow out’) is being increasingly used as an alternative to traditional ‘chemical relaxers’. It comprises of a protein keratin solution (containing formaldehyde, a known human carcinogen) infused into hair using heat. This leads to cross-linking of keratin amino acid side chains, resulting in straightened strands for up to 3 months.21 Gaseous release of formaldehyde during heating may cause eye, nose, throat and respiratory irritation, cough, chest pain and contact dermatitis.22 Thus unregulated use of this product poses potential health hazards to hairstylists and consumers.

Chemical relaxers Chemical hair straighteners’ were invented by Garrett Augusta Morgan, by chance, during an attempt to manufacture a sewing machine liquid lubricant.19 The liquid was incidentally found to penetrate the cortex and straighten the fibres of an old woolly cloth. This effect was duplicated on a curly haired dog and subsequently, Morgan’s own curly hair. By modifying the original formula, the first chemical relaxer was patented in 1913 and sold as G.A Morgan’s hair refiner.19 The original product has undergone numerous refinements since its introduction. Traditional salon hair relaxers are emulsions of 1.5–3.5% sodium hydroxide (lye).23 These are highly alkaline (pH 12–14) and corrosive agents. Thus, the most highly concentrated lye relaxers (Base lye relaxers) require a protective ‘base’ coat of petrolatum to be applied to the scalp prior to their application.24,25

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In an attempt to eliminate potential dangers associated with sodium hydroxide, milder, ‘no-lye’ relaxers containing potassium hydroxide, lithium hydroxide or guanidine hydroxide and ‘thio’ relaxers containing ammonium thioglycolate, were developed for home use. Despite the lower pH (pH 9-11), the relative alkalinity of these agents may still cause hair damage and scalp irritation. Lanthionization is the process by which hair is permanently straightened. Through the application of the aforementioned metal hydroxide emulsions to the hair, approximately one-third of cysteine residues are substituted for lanthionine with lower hydrolysis of peptide bonds.24 The high pH (9-14) causes swelling of the hair shaft, opening of the cuticles and exposure to the cortex and keratin. Disulphide bonds are broken thus denaturing the hair proteins and causing the hair strand to become flexible and stretched.24,26 The new straight shape is permanently fixed by rinsing the hair with an oxidizing agent delivered by a neutralizing shampoo that brings the hair back to its physiological pH. This step is imperative, as ongoing contact with the agent will cause complete disintegration of the hair strands. With the aim of restoring some of the moisture stripped off the hair during the straightening process, further rinsing with a conditioning shampoo is often a final step.25 Texturizing relaxers loosen the natural curl pattern without completely straightening the hair as a chemical relaxer would. They too contain sodium or lithium hydroxide and therefore also require rinsing with a neutralizing shampoo.27 Chemical straightening is not entirely permanent; new growth will possess the original disulphide bonds26 and for this reason, treatment of new growth may be desirable. Broadly speaking, this should take place at no earlier than 6–8 weeks post initial treatment and should only involve new growth, to avoid overlapping and hence damage to previously chemically treated hair.25,28,29

and lowered expectations.34 Hair straightening can thus be viewed as one of the many kinds of covering and shifting behaviours that allow people to manage their image to avoid discrediting themselves, especially in professional contexts.34 What is less widely acknowledged is that ‘looking better’ with straightened hair implies internalization of a hierarchy of appearance based on the superiority of naturally straight hair, an entrenched remnant of past social injustice.35 Hair straightening can be seen as one of the most common forms of ‘self-improvement’, which – along with skin lightening and surgery to reduce the prominence of ‘ethnic features’ – are at odds with the natural appearance of many people with afro-textured hair but which are readily adopted to facilitate social acceptance.34,35

Chemical straightening of afro-textured hair; clinical aspects There are many reported adverse effects associated with the use of chemical relaxers. These include scalp itch/irritation/burns or burning sensation, hair loss, hair breakage and change in hair colour.30,32,33 Hair breakage

The process of lanthionization replaces approximately one-third of the cysteine content of the hair fibre. This denaturation does not occur without a disruption in the structural strength of the hair fibres.33 When compared with untreated hair, Syed et al.36 found the tensile strength of chemically treated hair to be lower, with an associated increase in porosity, indicating damage. Khumalo et al.39 also found the cysteine levels of chemically relaxed afro-textured hair to be lower than that of natural hair. In particular, the cysteine content of distal chemically relaxed hair was similar to those found in patients with Trichothiodystrophy (TTD), a genodermatoses characterized by the presence of brittle fragile hair.38

Chemical straightening of afro-textured hair; sociological/anthropological factors Studies have shown that chemical straightening of afro-textured hair is practiced by an estimated 80% of African American women in the United States,30 and 49.2% of black women in Cape Town, South Africa.31 In addition, a Kenyan study showed that 59% of women currently wore relaxed hair, whilst 41% had previously relaxed their hair.32 The motivation for undertaking hair straightening in women with afro-textured hair are complex, but includes easier manageability of hair, perceived beauty, improved self-esteem and social acceptance (Dadzie OE, Salam A., submitted).32,33 Thus, when grooming choices are considered, women with afro-textured hair may feel that they do not have the luxury of choice because they live in societies where the dominant aesthetic norms for hair are the opposite of their natural condition. In many European, American and international business contexts, afro-textured hair is associated with negative stereotypes

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Figure 2 Central centrifugal Cicatricial Alopecia.

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Figure 3 Hair styling alternatives to chemical relaxers.

Chemical burns

Alkaline substances partially dissolve tissue proteins and produce burns through a process known as liquefaction necrosis.39 The caustic nature of such agents has the potential to cause scalp damage. This is especially true when high pH relaxers are left on the

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scalp for prolonged periods. ‘At-home’ hair relaxers are offending agents in paediatric cases of caustic ingestion.40 Although there is little evidence suggesting consequential oesophageal injuries, oral cavity and facial burns may occur.39,40 Corneal alkali burns have also been reported whilst rinsing chemical relaxers.41

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Table 1 Evidence-based data on the safe application of chemical relaxers Advice on the safe use of chemical relaxers

Level of evidence†

Application by professionally trained hairdressers24,28,51,52

V

Prior strand and porosity test to determine required processing time24,25,51

V

Processing time ideally no more than 20 min53

V

Scalp protection with a base coat of petrolatum25,28,38

V

Avoid concurrent traction associated hairstyles29,42

II

Have regular deep conditioning treatment51,53,54

V

‘Touch up’s’ of new growth only, no less than 6-8 weeks apart28,29

V

†American Society of Plastic Surgeons Evidence Rating Scales. Available at: http://www.plasticsurgery.org/Medical_Professionals/Health_Policy_ and_Advocacy/Health_Policy_Resources/Evidence-based_Guidelines Practice_Parameters/Description_and_Development_of_Evidence-based_ Practice_Guidelines/ASPS_Grade_Recommendation_Scale.html.

Alopecia

Chemical relaxers may be associated with hair loss either when used alone or in conjunction with traction-related hairstyles. In a recent cross-sectional study of women of African descent in London, UK, Dadzie et al. demonstrated that the use of chemical relaxers was significantly correlated with hair loss. However, this study did not specifically explore issues such as age of first use of chemical relaxers, or the type of ‘after-care’ employed by subjects who chemically relaxed their hair. Rucker et al.29 have shown that girls with chemically relaxed hair were twice as likely to report traction alopecia (TA), especially when combined with cornrows. Khumalo et al.42 have also confirmed this finding, demonstrating a higher odds ratio of hair loss when tractionrelated hairstyles are applied to chemically relaxed hair. Central centrifugal cicatricial alopecia (CCCA) (Fig. 2) is a primary lymphocytic cicatricial alopecia, affecting the crown and/or vertex.43–47 The aetiology of CCCA remains unknown, although hair grooming practices have been implicated including the use of hot comb and chemical relaxers.44,45,47 Recent data also links CCCA with the use of sewn-in weaves and artificial hair extensions. Dlova and co-workers have also recently demonstrated an autosomal dominant pattern of inheritance for CCCA, with hair grooming practices, such as use of chemical relaxers and traction-related hairstyles, affecting the expression of the disease.48 Other

There have been single case reports in relation to the occurrence of Steven–Johnson syndrome and irritant contact dermatitis complicated by deep-seated staphylococcal infection with the use of chemical relaxers.49,50 Interestingly, to the best of our knowledge, there are no reports of allergic contact dermatitis of the scalp induced by chemical relaxers.

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Conclusions Chemical hair straightening is a deep-seated cultural practice with potentially serious and long-term consequences for the health and appearance of the scalp and hair. Some patients may be receptive to discussion of alternatives to regular hair straightening (Fig. 3), but it is important that clinicians are sensitive to the needs expressed by many patients to continue to straighten their hair; in this setting counselling may be provided to patients on the safe use of chemical relaxers, bearing in mind that these recommendations are primarily based on expert opinions (Table 1). Public health campaigns targeting this cohort are also required to educate women on the safe use of chemical relaxers, as well as educating them on alternative ‘scalp friendly’ hairstyles.

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Clinical and anthropological perspectives on chemical relaxing of afro-textured hair.

The culturally engrained practice of 'relaxing' afro-textured hair has been linked with hair and scalp disorders. Herein, we discuss the evolution of ...
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