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With more than 20 countries to explore, Asian travel tours offer something for everyone. Sample coconut soup and crispy fried noodles from a street vendor in Bangkok. Experience the bustle of Tokyo and Singapore or relax on a beautiful beach in Borneo or Bali. Find adventure climbing a mountain in the Himalayas or riding an elephant in India.
Asian hair is known for its straightness, dark pigmentation, and large diameter. The cuticle layer in Asians is thicker with more compact cuticle cells than that in Caucasians. Asian hair generally exhibits the strongest mechanical properties, and its cross-sectional area is determined greatly by genetic variations, particularly from the ectodysplasin A receptor gene. However, knowledge on Asian hair remains unclear with limited studies.
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This article aimed to review and summarize the characteristics and properties of Asian hair. It also aimed to discuss hair disorders including linear lupus panniculitis and pseudocyst of the scalp that occur distinctively in Asian populations. The diversity Single asian girls Sulphur human hair is the result of different genetics and demographic backgrounds together with hair grooming and cultural practices.
Understanding the differences in hair morphologies, structures, and properties among various populations is important for clinicians to provide a correct diagnosis and treatment as hair disorders present and progress differently. Human hair is generally categorized into three major groups according to ethnic origins, ie, Asian, African, and Caucasian. Each ethnic group possesses different hair features including hair thickness, curvature, pigmentation, and mechanical properties. Currently, knowledge on Asian hair remains unclear due to limited studies.
This review aimed to summarize the characteristics and properties of Asian hair and present hair disorders exclusively described in Asian population. Hair in Asian population shows a distinctive appearance of being straight, round, and having black or brown pigmentation. The comparisons of hair characteristics among the three major ethnic groups are summarized in Table 1. Note: Information provided in Table 1 is summarized from references 2—8. Hair shaft, mainly Single asian girls Sulphur up of keratin materials, consists of three layers, namely, the cuticle, cortex, and occasionally medulla.
The medulla is located at the center, surrounded by the cortex, which is the principal structure of the hair shaft.
The cuticle is the outermost layer that functions as a barrier against physical and chemical damage. The cuticle layers are composed of multiple sheaths of flat overlapping cells and cell membrane complex CMC between the cuticle cells. Moreover, the African hair shows a higher incidence of cuticle damage. With regard to the cortex of the hair shaft, cortical cell structures generally comprise macrofibrils, remnants, and pigment granules. Macrofibrils are the major components made up of intermediate filaments IF or microfibrils, which are cross-linked with keratin-associated proteins and embedded in the amorphous materials called matrix.
Asian hair has the greatest cross-sectional area among the three human hair types. African and Caucasian hairs have relatively equal cross-sectional areas that are smaller than Asian hair. Genetic studies found that hair thickness in Asian populations is linked to genetic variations. Fujimoto et al observed a correlation between a nonsynonymous single nucleotide polymorphism SNP in ectodysplasin A receptor EDAR gene and hair thickness in Asians in a genome-wide analysis.
ValAla and shows a strong positive selection in Asians in several studies. Hair curvature is greatly diverse among different ethnic populations. In contrast to African hair that is more Single asian girls Sulphur and often has twists Single asian girls Sulphur turns, Asian hair tends to be round in shape, straight, and more cylindrical.
There are multiple proposed mechanisms of hair curvature: uneven expression of hair keratins in the precortex; asymmetrical distribution of proliferating cells and unbalanced proliferative compartment of the hair follicle; uneven bilateral distribution of cortical cell types that are determined by the different arrangements of IF inside the cortical cells; inner root sheaths incorporated in shaping hair fiber; and differences in dermal papilla shape that influences hair curl.
Hair straightness is one of the morphological features that are diverse among races, implying an influential genetic linkage. A genome-wide analysis in admixed individuals with eastern and western ancestries Uyghur population revealed that EDAR can explain hair straightness variation better and has a greater effect than TCHH.
No interaction was found between these two genes, Single asian girls Sulphur their effects on hair straightness through different mechanisms. The diversity of hair pigmentation, as well as skin color, mainly from various amounts of admixed eumelanin and pheomelanin. Dark hair contains a high level of eumelanin and a small level of pheomelanin.
Asian hair: a review of structures, properties, and distinctive disorders
Blond hair contains a low level of eumelanin and a trace of pheomelanin, whereas red hair has low to medium levels of both eumelanin and pheomelanin. The dark pigmentation is mostly determined by an eumelanin production from melanocytes residing in the basement membrane encircled by the dermal papillae. Losing a melanocortin 1 receptor MC1R function from the mutation le to pheomelanin overproduction and red hair color phenotype.
The high degree of polymorphisms in human MC1R had been reported, but an ArgGln variant was detected only in Asian, Indian, and African-Indian populations with great differences in frequency. Size and density of melanosomes in a hair fiber contribute to hair pigmentation.
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Black hair has the largest melanosome and tightly packed eumelanin content. Brown hair has a smaller melanosome with ellipsoid shape. Asian hair shows the fastest growth rate in comparison to the other two hair types. African hair has the lowest growth rate. Hairs with larger cross-sectional area grow faster and have a shorter cuticle interscale distance, and vice versa.
This relationship was reported in Asians and Caucasians with straight or semi-straight hairs. Hence, it can be inferred that a Single asian girls Sulphur hair would grow with a different rate correspondent to various cellular division rates in the convex and concave parts. InFranbourg et al found that African hair has a lower radial swelling percentage in water compared with Asian and Caucasian hairs, which le to a possibility of lipid differences among ethnic hair types.
Hair lipid components can be separated into internal and external lipids according to their origins. Internal lipids are biosynthesized inside the hair matrix cells and mostly comprise free fatty acid FFAcholesterol, and polar components, such as ceramide, cholesterol ester, and cholesterol sulfate.
External lipids, including sterol esters and squalene, are known to arise from the surface sebaceous lipids.
Experimental showed that among the three ethnicities, African hair has the largest amount of total hair lipid extractions, followed by Caucasian and Asian hairs. Integral hair lipids located in the CMC of hair cuticle layers are able for hair integrity, maintenance of hydrophobicity, moisture, and hair stiffness. All three hair origins similarly show a smaller amount of lipids in the cortex compared with the cuticles.
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In addition, Takahashi and Yoshida detected glycoside-like lipids particularly N-acetyl glycoside in Japanese female hairs at the interface between the cuticle and the cortex producing an adhesive effect between the two layers. The alpha-linoleic acid-derived oxidative metabolites incorporate tightly in the melanin granules, implying the possibility of their participation during melanosome synthesis and melanogenesis.
Among human races, Caucasian fiber is the most hydrated one, which is different from African and Asian hairs that relatively have similar moisture content.
When the lipid was extracted, Caucasian hair was shown to have the greatest decreased hydration despite higher contents of lipid extraction in African fiber. Asian and African hairs share the same reduction level in moisture content. The diminution of water was speculated to be related to lipid saturation degree or the internal lipid content rather than the total amount of lipids.
As the lipids are involved in keratin conformation, they may contribute to hair tensile strength. Mechanical properties vary among different ethnicities. Asian hair demonstrates the highest hardness and elastic modulus, followed by Caucasian and African hairs, respectively. All three hair types that were studied in this research presented a decrease of both properties at the hair tip due to cuticle damage. It requires Single asian girls Sulphur earliest breaking time and a lower stress at breaking.
With regard to the influence of hair size, Asian and Caucasian hairs exhibit similar response to stress and strain even though Asian hair has a bigger cross-sectional area. Stretching of hair can distort hair structure as well as its properties. A study conducted on Asian and Caucasian hair samples observed the elevated level of cysteine residues, indicating disulfide bond ruptures from cysteine oxidation during the stretching process.
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The disordered content in Caucasian hair is raised at lower stretching ratios compared with that in Asian hair. Chemical products, such as hair bleaching and hair dye, can alter hair shaft morphology and its properties. The cortex from the three major ethnic groups shows a similar response to straightening and coloring treatment, but African hair exhibits greater tolerance to combination treatment straightening and coloring.
Hairs from all studied ethnic groups demonstrate similar patterns of CMC damage after straightening and combination treatment, but Asian hair displays a bulged CMC and has lesser endurance than the others after treatment of coloring Single asian girls Sulphur.
Diagnosis and management of hair and scalp disorders have always been a challenge for dermatologists. Increasing evidence suggests that the prevalence, as well as clinical presentation and severity of diseases, vary greatly among different ethnicities. This section discusses the different characteristics of common and distinct hair disorders in Asian populations.
Alopecia areata affects 0. The mean age of onset is similar to Caucasians. Family history and vitiligo in Asians are lesser associated compared with the Westerners, but the percentages of autoimmune thyroid diseases are comparable.
Tinea capitis is another common hair problem worldwide and is caused by Trichophyton and Microsporum spp. Etiologic agents diversely depend on the regions.
In Asians, the most common causative organisms are Trichophyton ferrugineum and Trichophyton violaceum. The triglyceride-rich sebum production in adults was hypothesized to have a fungistatic effect creating a greater innate protection against ecthotrix fungal infections and a lower prevalence compared with that in children.
Other contributing factors to fungal infection are hair care practices. A low frequency of shampooing links to decreased spore disposal. The traction hairstyle in Africans allows easier access to fungus. Scarring or cicatricial alopecia from irreversible injury of follicular stem cells and replacement of hair follicles with fibrous tissues Single asian girls Sulphur hyalinization of collagen. Primary scarring alopecia PSA is characterized by an idiopathic folliculocentric inflammation that le to a permanent hair follicular destruction. Secondary scarring alopecia is caused by inflammatory infiltrates of scalp skin that damage their nearby hair follicles.
Neutrophilic PSA also occurs more in men, but mostly in their middle age. Unlike Asians, Caucasians are dominated with lymphocytic PSA, eg, lichen planopilaris and chronic cutaneous lupus erythematosus. The curly and frizzy hair of African populations, together with markedly curved hair follicles and manipulation cause hairs to curl back into Single asian girls Sulphur dermis, which then le to a foreign-body reaction. Given the lower hair tensile strength combined with the high degree of curl and dryness, African hair fibers are more vulnerable to damage from daily traction-producing hair cares compared with Asian hair.